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The midblock pedestrian signal (MPS) operates as a coordinated actuated vehicular traffic signal that enables pedestrians to cross at midblock. The MPS has been used in multiple locations, including for more than 40 years in Los Angeles. It differs from a typical pedestrian crossing signal by allowing the red display for vehicular traffic to flash at the same time as the pedestrian timing for the crossing, reducing delay to vehicular traffic. The research team built a database of crash and roadway characteristics data for treated and control sites located in three states (California, Utah, and Texas). Three control groups were considered: all control sites (included intersections with two, three, or four legs and traffic control signals); two-leg sites with any type of pedestrian traffic control other than the MPS; and two-leg sites with nonactive or not present pedestrian traffic control devices. It was found that the MPS is associated with a reduction in the number of crashes involving pedestrians and a reduction in the number of all fatal and injury crashes when the control group is two-leg sites with nonactive or not present pedestrian traffic control devices. The following crash modification factors for the MPS were identified: 0.554 for crashes involving pedestrians; and 0.660 for all crashes.

An effective access management technique can improve both traffic safety and operation along a roadway corridor while maintaining a reasonable level of access to the adjacent properties. Even though raised medians enhance traffic operation and safety by minimizing the number of turning movements at mid-block locations, they shift the potential turning maneuvers to the nearby intersections. Moreover, raised medians have negative economic impacts on the adjacent business owners. Therefore, providing a median opening along a corridor should be evaluated as a trade-off between the gains and losses and installed where the benefits outweigh the potential drawbacks. There is no guideline available that specifically focuses on a median opening in the proximity of a signalized intersection. Therefore, this paper evaluated the safety and operation of the median openings nearby signalized intersections as well as determining the variables that influence the performance of the median openings. The results indicated that the minimum required distance from a median opening to its adjacent signalized intersection is influenced by the number of conflicting driveways, median opening type, and the number of arterial lanes. Moreover, the safety at a median opening is dependent on the median opening type, the number of arterial lanes, and average daily traffic. The results could help transportation agencies to analyze how installing a median opening nearby a signalized intersection affects both traffic safety and operation.

To address public health concerns about rising pedestrian–vehicle crashes, traffic agencies are seeking options to reduce the number and severity of crashes. For established pedestrian-crossing locations, an increasingly common traffic-control treatment is the pedestrian- or school-crossing warning sign with light-emitting diodes (LEDs) embedded in the borders (called LED-Em in this paper). The LED-Em treatment, a system that includes LEDs embedded in warning signs and pedestrian push buttons, is pedestrian activated, so the LEDs only flash when a pedestrian is attempting to cross the street. For this analysis, researchers considered more than 7,000 drivers involved in more than 3,200 staged pedestrian crossings at 53 sites. The average driver-yielding rates at those sites were analyzed, using analysis of covariance models to assess the effects of various roadway characteristic variables as well as traffic-control device characteristic variables. The statistical analysis showed that the posted speed limit and the vehicle volume at the time of the crossing influenced a driver’s decision to yield to a pedestrian attempting to cross a street when an LED-Em treatment was present. Higher posted speed limits and higher vehicle volumes were associated with lower driver yielding.

The operation and design of signalized intersections involves tradeoffs between operational efficiency and safety for a variety of users, including motorists, pedestrians, and bicyclists. Additionally, the mix of vehicle types in the fleet sometimes requires special considerations. These concerns especially apply to the selection of curb radius at the corners, where right-turning vehicles operate close to pedestrians. Larger curb radii accommodate the swept paths of trucks and allow right turns to occur at higher speeds but may compromise safety and security for pedestrians by increasing the crossing distance and increasing the frequency of higher-speed turns. The authors collected right-turn vehicle speeds at 31 urban signalized intersection approaches in Texas with radii ranging from 15 to 70 ft. The authors calibrated a model to predict right-turn speeds as a function of site characteristics including curb radius, leading headway, vehicle type (car versus truck), maneuver of the preceding vehicle (through versus right turn), and signal indication (yellow or green). The analysis results indicate that right-turn speeds increase slightly with increasing radius, if the preceding vehicle proceeds through (rather than turning right) at the intersection, or if the signal indication is yellow rather than green. The calculated 85th percentile turning speed is generally higher than the assumed speed calculated using the radius of curvature equation. These trends should be considered if the intersection is expected to have notable volumes of pedestrians or trucks, as lower speeds are desirable for pedestrian safety, but larger radii may be necessary to accommodate turning trucks.

The National Cooperative Highway Research Program (NCHRP) Project 17-76 investigated factors that influence operating speed and safety through a review of the literature and an analysis of the relationships for speed, safety, and roadway characteristics on urban/suburban streets. That knowledge, along with a review of existing speed limit setting practices, was used to develop a Speed Limit Setting Procedure (SLS-Procedure) as well as a user manual to explain the SLS-Procedure. In addition, the SLS-Procedure was automated via a spreadsheet-based Speed Limit Setting Tool (SLS-Tool). These products will permit engineers to make informed decisions about the setting of speed limits. The SLS-Procedure is fact based and transparent, relying on a set of decision rules that consider both driver speed choice and safety associated with the roadway. The SLS-Procedure was designed to be applicable across different roadway types and contexts by having a set of unique decision rules for four combinations of roadway types and contexts: limited-access, undeveloped, developed, and full-access facilities. The SLS-Procedure uses the operating speed distribution as a starting point for the suggested speed limit, with the resulting suggested value based on consideration of roadway type, context, safety performance, and other characteristics.

To date, the effectiveness of light emitting diode (LED)-embedded pedestrian crossing signs is not understood, despite such signs being installed and used at pedestrian crossings. A recent study by Texas Department of Transportation focused on examining driver yield rates, a surrogate safety measure, for signs installed across the state. A total of 13 sites were sampled and field observations and video footage were recorded at each site for a total of 681 staged crossings. The driver yield rate ranged from 5% to 88%, with an average of 40%, indicating that other factors affect the effectiveness of the signs. Statistical modeling results supported this finding with the main contributors to driver yield rates being vehicle volume, measured at 1 min before the staged pedestrian crossing (converted to an hourly volume for the model), operational speed (85th percentile), deviation from 12-ft lane width, and presence of sidewalk. High hourly volume, speeds 45 mph and greater, lack of sidewalks, and 12-ft lanes (no deviation from baseline 12-ft lane width) were found to affect yield probability adversely. Based on the findings from this study, LED-embedded signs would be a suitable candidate treatment at sites with sidewalks, lower operating speeds and traffic volumes, and narrow lanes. Lastly, a comparison between driver yield rates for rectangular rapid flashing beacons, pedestrian hybrid beacons, and LED-embedded signs for various posted speed limits demonstrated that, of the three treatments, LED-embedded signs have the lowest driver yield rates, especially for higher posted speed limits.

Safety analysts are generally interested in understanding the differences in the safety performance when a two-way street is converted to a one-way operation or vice-versa. Literature exists to understand and predict the safety of two-way streets. However, safety prediction procedures are currently not available for assessing the safety performance of one-way arterials. This research was undertaken to develop safety prediction models for one-way arterials. To accomplish this objective, data collected in California, Illinois, Michigan, Oregon, and Texas were assembled that included a wide range of geometric design features, traffic control features, traffic characteristics, and crash records. The data were used to calibrate predictive models, each of which included a safety performance function (SPF) and several crash modification factors (CMFs). Separate SPFs were developed for fatal and injury crashes (i.e., fatal, incapacitating injury, non-incapacitating injury, and possible injury crash) and property-damage-only crashes. The SPFs were estimated using the negative binomial modeling structure. Severity distribution functions (SDFs) were also calibrated using the fatal and injury data. These functions can be used with the predictive models to estimate the expected crash frequency for each of four injury severity levels.

Pedestrian fatal crashes in the U.S. have increased over the years. From 2007 to 2016, pedestrian fatalities increased 27% nationally, while all other traffic fatalities decreased 14%. On average, a pedestrian was killed every 1.5 h in traffic crashes in 2016. The Federal Highway Administration (FHWA) has been working with public agencies toward developing more data-driven approaches to identify and mitigate pedestrian safety issues. However, pedestrian exposure to risk is not readily available. The absence of pedestrian exposure data makes it challenging to identify and prioritize high-crash risk locations. Using Dallas, Texas, as a case study, researchers wanted to use exposure in relation to volumes—both vehicular and pedestrian volume—to determine pedestrian risk. Although the vehicular volume is extensively available, the pedestrian volume is seldom available. The objective of this study is to explore options for collecting or estimating pedestrian volume data, particularly at intersections with high pedestrian activity. Researchers successfully developed a direct-demand model that estimates pedestrian volumes at signalized and stop-controlled intersections. The final model showed that pedestrian volume: increases 4 times within downtown; increases 12% per school within 1 mi of intersection; increases 4.8 times per 1% increase in commercial/multi-family residential land uses within 300 ft of intersection; increases 4.7 times with presence of higher education, hospitals, or malls; and decreases 36% per 5 mph increase in the intersections’ maximum posted speed limit. This research can help advance pedestrian safety analyses by providing a method of estimating pedestrian volumes for intersections by control type, particularly when volumes are infeasible to measure.

Increased traffic and heavy truck percentages associated with energy exploration in West Texas have placed unprecedented demands on the region’s highway network as well as driveway access to and from that network. Access management principles have proven to be effective in improving operations and safety in numerous locations, but many of those locations have been in urban or suburban locations where land uses and traffic patterns are different from those typically found in rural West Texas, so guidelines for driveway spacing and other access management treatments in rural, high-speed areas are not as commonplace. This paper describes the study of a corridor with high volumes, high truck percentages, high speeds, high turning volumes, and high demand for access. The study team reviewed the applicable guidelines and policies for driveway spacing in Texas, as well as relevant findings from other guidelines and research, to develop a set of recommended driveway spacing values for cars and for trucks on high-speed rural roads.

The pedestrian hybrid beacon (PHB) is a traffic control device used at pedestrian crossings. It was first included in the 2009 Manual on Uniform Traffic Control Devicesand was based on the HAWK developed in Tucson, Arizona. The focus of an Arizona Department of Transportation research study was the investigation of the use of PHBs on higher-speed roads. Ten locations in Arizona representing higher operating speed conditions (85th percentile speed ranging from 44 to 54 mph) were selected for inclusion in this study. Data were collected using a multiple video camera setup. The final dataset reflected about 40 h of video data and included 1,214 pedestrians or cyclists crossing at PHBs. Overall, driver yielding for these 10 sites averaged 97%, which is similar to driver-yielding rates for PHBs installed on lower-speed streets.

The 2009 United States Manual on Uniform Traffic Control Devices(MUTCD) includes guidance for the use of various types of traffic control at unsignalized intersections. Despite changes and advances in traffic engineering in recent decades, the MUTCD content related to selection of traffic control in Part 2B has seen only minor changes since 1971. The types of unsignalized traffic control addressed in the current research included no control, yield control, two-way stop control, and all-way stop control. The research team developed recommendations using information available from reviews of existing literature, policies, guidelines, and findings from an economic analysis along with the engineering judgment of the research team and panel. The researchers then developed recommended language for the next edition of the MUTCD for unsignalized intersections. This includes consideration of high-speed (rural) and low-speed (urban) conditions along with the number of legs at the intersection. Because the number of expected crashes at an intersection is a function of the number of legs, the decision on appropriate traffic control should also be sensitive to the number of legs present. The proposed language includes introductory general considerations, discusses alternatives to changing right-of-way control, and steps through the various forms of unsignalized control from least restrictive to most restrictive, beginning with no control and concluding with all-way stop control.

Estimates from the U.S. Census Bureau indicate that the elderly (age 65 and older) people represented 12% of the total population in 2005. Bicycling is becoming popular among people of all groups. In 2016, 130 elderly bicyclists were killed (20% higher than 2014) on the U.S. roadways. The sharp rise of elderly bicyclist fatal crashes calls for a rigorous study to determine the key associated factors in elderly bicyclist crashes. Graphical methods, such as joint correspondence analysis (JCA), are useful in identifying the association patterns from a complex data set with multiple variables by producing a proximity map of the variable categories in a low dimensional plane. This study used 3 years (2014 to 2016) of data on elderly bicyclist fatal crashes from the Fatality Analysis Reporting System (FARS) in the U.S. to determine the key associations between the contributing factors by using JCA. Some of the key findings include bicyclist fatal crashes on roadways with high posted speed being very random; higher crash occurrences on roadways with bicycle lane/shoulder/parking lane under dark conditions with no lighting, on two-way undivided roadways with bicyclists on the travel lane, and at signalized intersections (pedestrian/bicycle signal presence is unknown) with “motorists fail to yield” related crashes. The findings from the current study can help in refining the policies and safe design practices that explicitly recognize this issue and will better serve a growing segment of the nation’s population.

A recent survey conducted by the National Committee on Uniform Traffic Control Devices Task Force explored current and potential approaches to the setting of posted speed limits. The survey was distributed in the spring of 2018 and gathered 740 responses. The survey found that many states and local agencies have their own laws or criteria for the setting of speed limits (many are very detailed). Professionals who perform posted speed limit studies rarely onlyuse the 85th percentile speed. It is clear from the survey that analysts who establish speed zones utilize many factors beyond the 85th percentile in their studies, including the context, that is, where the street is and what function it serves. The use of the 85th percentile for rural roads or interstate/freeways is different from urban streets (on urban streets, the 85th percentile plays a less significant role). The industry knowledge and use of USLIMITS2 are very limited. USLIMITS2 is a web-based tool designed to help practitioners set speed limits and is maintained by the Federal Highway Administration. Setting of reasonable speed zones requires consideration of many factors that are currently not well defined in the Manual on Uniform Traffic Control Devices(MUTCD). These factors are best defined as part of national guidance/research or local policy documents and do not need to be defined in the MUTCD as they can involve state/local interpretation.

This paper investigated the safety implications of managed-lane cross-sectional elements. The objective of the Federal Highway Administration project was to investigate the relationship between crashes and buffer-separated managed lane dimensions. The results from several previous research studies have demonstrated that reductions in freeway lane width or shoulder width are associated with more crashes. This research found that a narrower managed-lane envelope width (i.e., left shoulder, managed-lane, and buffer width combined) is also associated with more freeway crashes for crashes of all severity levels including fatal and injury. Wider envelopes are associated a reduction in total freeway crashes, of all severities, of 2.8% in Texas, and 2.0% in California, for each additional foot of envelope width. In California, wider envelopes are associated with a reduction of 4.4% in managed-lane-related crashes resulting in fatalities and injuries at all severity levels, for each additional foot of envelope width. The analysis was conducted on nonweaving managed-lane segments that included a single managed-lane separated from the general-purpose lanes with a flush buffer area. The dataset included crashes on 128.0 miles of freeway in California (all 128.0 miles with flush buffers) and 60.4 miles of freeway in Texas (41.7 miles with pylon buffers and 18.7 miles with flush buffers). The California sites included freeways with three or four general-purpose lanes, and the Texas freeways had three to five general-purpose lanes.

Chapter 3 in the 2004 AASHTO high-occupancy-vehicle guidelines includes a prioritized trade-off table of various design options for high-occupancy-vehicle lanes (now known as managed lanes). The design trade-offs include the reduction of lane, shoulder, or buffer width. The key measure thought to be affected by lane, shoulder, and buffer width is lateral position. The presented study identified the relationship between operations and cross-section width, including the type of buffer design separating the managed lanes from the general-purpose lanes. This research study collected lateral position data on existing managed lane facilities with a range of geometric elements within both tangent and horizontal curves and identified potential relationships between the geometric design element values and the measure of effectiveness. The field studies included data collected at 28 sites with fixed video cameras and along 161 centerline miles with an instrumented vehicle that recorded data for the vehicle immediately in front of the instrumented vehicle. The study found that managed-lane drivers shifted away from the pylons placed in the buffer. Horizontal alignment (tangent or curve) and the direction of the horizontal curve (left or right) influenced lateral position. Left shoulder, lane, and buffer width affected lateral position. Modifying a 6.5-ft shoulder to a minimum shoulder (i.e., 1.5 ft) will result in drivers moving to the right about 0.5 ft; however, if an 18.5-ft shoulder is reduced by 5 ft, the impact in operations is negligible (drivers would shift only about 0.11 ft toward the right).

Managed lanes typically are on or adjacent to freeways and are actively operated and managed to preserve operational performance—such as more optimal travel speeds—over comparable general-purpose traffic lanes. A study was conducted to evaluate speeds on existing buffer-separated managed lanes to identify variables that influence operating speed. Speed data from more than 130 unique sites in Los Angeles, California; Orange County, California; and Dallas, Texas, were used. All analyses showed that the managed lane volume and the speed in the general-purpose lanes were related to the speed in the managed lane (statistically significant). The Dallas analysis, which used speeds averaged by 1-min increments, showed that the factor with the most influence on uncongested managed lane speed was the managed lane’s geometry. The relationship between uncongested managed lane speed and the managed lane envelope (sum of left shoulder width, managed lane width, and buffer width) was found to be statistically significant. For each additional foot over a 16-ft envelope width, managed lane speed increased by approximately 3.2 mph. In contrast, the California analysis, which used speeds averaged by 1-h increments, showed that the variable having the most influence was the volume in the managed lane. The researchers theorized that the lack of a relationship between managed lane speed and geometry in California is related to those speeds being an average 1-h speed rather than the 1-min speeds available in Texas.

Previous studies of rectangular rapid-flashing beacons have found a wide range of driver yielding rates (19% to 98%). As part of the efforts to study yielding at different types of crosswalk locations better, this research compared alternative statistical methods to analyze staged crossing data. A database was compiled of 12,040 individual crossings at 73 sites representing 128 crossing periods, which included a set of 27 potentially influential variables. Analysis of this data set began with considering the hypothesis that negative binomial regression could be the most appropriate method of analysis, given the characteristics of the data collected at each staged crossing. However, alternative methods—in particular, logistic regression and analysis of variance—also appear appropriate. Even when these alternative methods may not explicitly account for some theoretical implications of staged-crossing data, the methods may prove to model yielding rates acceptably. A potential benefit of using the alternative methods is that the results may be easier to interpret in the context of decision making in regard to pedestrian crosswalk treatments. This research investigated the methodological aspect of analysis to advance the understanding of the explanatory factors, the results, and the phenomena under study. Results from various analyses indicated that logistic regression tended to yield results that were more accurate. Additionally, this research found that the statistical power of two of the techniques evaluated increased when explicitly accounting for the total number of cars observed at each crossing.

Increasing volumes, specifically heavy truck volumes, have an increasingly greater effect on operations on the nation’s two-lane highways. Various strategies have been implemented to reduce delay and increase capacity, particularly the use of marked passing zones and the addition of periodic passing lanes to allow faster vehicles to pass slower vehicles and to disperse platoons. However, much existing guidance and previous research focused on those design features in the context of passenger vehicles. As the volume of heavy vehicles increases, particularly in high-demand corridors such as those related to energy exploration or manufacturing distribution, so does the number of individual trucks and truck convoys that can further erode operational characteristics on two-lane highways. This paper summarizes existing guidance and recent literature on passing treatments and design guidelines for passing sight distance, passing lanes, and passing zones. This paper also presents results from a proof-of-concept exercise to demonstrate potential effects of trucks on extending the lengths of passing sight distance for certain scenarios.

Previous studies of rectangular rapid-flashing beacons have found a wide range of driver yielding rates (19% to 98%). As part of the efforts to study yielding at different types of crosswalk locations better, this research compared alternative statistical methods to analyze staged crossing data. A database was compiled of 12,040 individual crossings at 73 sites representing 128 crossing periods, which included a set of 27 potentially influential variables. Analysis of this data set began with considering the hypothesis that negative binomial regression could be the most appropriate method of analysis, given the characteristics of the data collected at each staged crossing. However, alternative methods—in particular, logistic regression and analysis of variance—also appear appropriate. Even when these alternative methods may not explicitly account for some theoretical implications of staged-crossing data, the methods may prove to model yielding rates acceptably. A potential benefit of using the alternative methods is that the results may be easier to interpret in the context of decision making in regard to pedestrian crosswalk treatments. This research investigated the methodological aspect of analysis to advance the understanding of the explanatory factors, the results, and the phenomena under study. Results from various analyses indicated that logistic regression tended to yield results that were more accurate. Additionally, this research found that the statistical power of two of the techniques evaluated increased when explicitly accounting for the total number of cars observed at each crossing.

Managed lanes typically are on or adjacent to freeways and are actively operated and managed to preserve operational performance—such as more optimal travel speeds—over comparable general-purpose traffic lanes. A study was conducted to evaluate speeds on existing buffer-separated managed lanes to identify variables that influence operating speed. Speed data from more than 130 unique sites in Los Angeles, California; Orange County, California; and Dallas, Texas, were used. All analyses showed that the managed lane volume and the speed in the general-purpose lanes were related to the speed in the managed lane (statistically significant). The Dallas analysis, which used speeds averaged by 1-min increments, showed that the factor with the most influence on uncongested managed lane speed was the managed lane’s geometry. The relationship between uncongested managed lane speed and the managed lane envelope (sum of left shoulder width, managed lane width, and buffer width) was found to be statistically significant. For each additional foot over a 16-ft envelope width, managed lane speed increased by approximately 3.2 mph. In contrast, the California analysis, which used speeds averaged by 1-h increments, showed that the variable having the most influence was the volume in the managed lane. The researchers theorized that the lack of a relationship between managed lane speed and geometry in California is related to those speeds being an average 1-h speed rather than the 1-min speeds available in Texas.

Chapter 3 in the 2004 AASHTO high-occupancy-vehicle guidelines includes a prioritized trade-off table of various design options for high-occupancy-vehicle lanes (now known as managed lanes). The design trade-offs include the reduction of lane, shoulder, or buffer width. The key measure thought to be affected by lane, shoulder, and buffer width is lateral position. The presented study identified the relationship between operations and cross-section width, including the type of buffer design separating the managed lanes from the general-purpose lanes. This research study collected lateral position data on existing managed lane facilities with a range of geometric elements within both tangent and horizontal curves and identified potential relationships between the geometric design element values and the measure of effectiveness. The field studies included data collected at 28 sites with fixed video cameras and along 161 centerline miles with an instrumented vehicle that recorded data for the vehicle immediately in front of the instrumented vehicle. The study found that managed-lane drivers shifted away from the pylons placed in the buffer. Horizontal alignment (tangent or curve) and the direction of the horizontal curve (left or right) influenced lateral position. Left shoulder, lane, and buffer width affected lateral position. Modifying a 6.5-ft shoulder to a minimum shoulder (i.e., 1.5 ft) will result in drivers moving to the right about 0.5 ft; however, if an 18.5-ft shoulder is reduced by 5 ft, the impact in operations is negligible (drivers would shift only about 0.11 ft toward the right).

Increasing volumes, specifically heavy truck volumes, have an increasingly greater effect on operations on the nation’s two-lane highways. Various strategies have been implemented to reduce delay and increase capacity, particularly the use of marked passing zones and the addition of periodic passing lanes to allow faster vehicles to pass slower vehicles and to disperse platoons. However, much existing guidance and previous research focused on those design features in the context of passenger vehicles. As the volume of heavy vehicles increases, particularly in high-demand corridors such as those related to energy exploration or manufacturing distribution, so does the number of individual trucks and truck convoys that can further erode operational characteristics on two-lane highways. This paper summarizes existing guidance and recent literature on passing treatments and design guidelines for passing sight distance, passing lanes, and passing zones. This paper also presents results from a proof-of-concept exercise to demonstrate potential effects of trucks on extending the lengths of passing sight distance for certain scenarios.

The pedestrian hybrid beacon (PHB) has shown great potential in improving safety and driver yielding; however, questions have been asked about actual driver and pedestrian behavior. A data set reflecting more than 78 h of video data recorded at 20 locations included 1,979 pedestrians crossing during 1,149 PHB actuations. For the 20 sites, driver yielding to pedestrians averaged 96%. For the majority of the pedestrians who left during the dark indication (124 of 1,979, which was 6%), the roadway volume was such that the pedestrian was able to find sufficient gaps (fewer than four vehicles/min/lane for the majority of these crossings). Overall, 91% of the pedestrians pushed the pushbutton. A greater number of pedestrians activated the device on a road with a posted speed limit of 45 mph compared with roads with a posted speed limit of 40 mph or less. When the equivalent hourly volume was 1,500 vehicles/h or more, the percentage of pedestrians activating the PHB was always 92% or more. The conflict rate was found to be higher for noncompliant pedestrians than for compliant pedestrians. More conflicts occurred at locations with nearby bus stops or driveways.

Distraction has been a point of interest in transportation research for many years. Recently, this interest has extended from distracted drivers to distracted pedestrians. Past research suggests that distracted pedestrians are less likely to show cautionary crossing habits and tend toward increased crossing times. This study provided information about the pedestrian waiting to cross and investigated how distraction and other factors may have affected pedestrian start-up time and crossing behaviors. Researchers surreptitiously observed 760 pedestrians at three intersections in College Station, Texas, and coded their characteristics and behavior in real time. Characteristics recorded were age, gender, distraction, and grouping. Distractions recorded were talking on a phone, texting, listening to music, eating, drinking, smoking, and other. The pedestrian groups were no group (crossed alone), mixed-age group, and peer group. Behaviors recorded were glancing before entering the crosswalk, entering the crosswalk early, walking within the crosswalk markings, and hurrying across the crosswalk. Pedestrians who texted and pedestrians who talked on a phone had 21% and 31% more start-up time, respectively. Additionally, pedestrians in mixed-age groups had 14% more start-up time. Texting pedestrians were about two times less likely to glance before entering the crosswalk compared with undistracted pedestrians. Similarly, a pedestrian engaged in a phone conversation was about five times less likely to glance. These results may provide insight into ongoing discussion on how to address distracted pedestrians crossing the street.

This research effort identified the operational and safety implications of the use of reduced lane and shoulder widths for a variety of urban freeway configurations. The study used speed, crash, and geometric data for freeways in Dallas, Houston, and San Antonio, Texas. The operational analysis identified an increase of about 2.2 mph in speed for a 12-ft lane compared with an 11-ft lane. The shoulder width is significant when the adjacent lane is 11 ft wide, but not when it is 12 ft wide. These findings suggest that the width of the left shoulder is more important with a reduced lane width. Operating speeds on Texas freeways are 2 mph lower during nighttime (with roadside lighting present) than during the day. Speeds were higher (by 1.5 mph) on the weekends (Saturday) than on the weekday studied (Wednesday). The safety analysis determined a crash difference when freeways with 12- to 11-ft lanes were compared. There was a reduction in fatal and injury crashes that ranged from 5% for two-lane freeways up to 12% for five-lane freeways. Similarly, some crash reductions were associated with each additional lane, increased left shoulder widths, and increased right shoulder widths. This paper concludes with a series of sample problem scenarios that collectively demonstrate how the resulting operating speed and crash prediction models allow practitioners to assess the trade-offs that can be expected when urban freeway lane and shoulder widths are modified.

Several methods have been used to emphasize the presence of a pedestrian crossing, including supplementing signing with beacons. A device that has received national attention is the rectangular rapid-flashing beacon (RRFB). A question being asked is whether the position of the beacons above or below the pedestrian crossing sign influences the effectiveness of the treatment. A closed-course study found that at night RRFBs located above the crossing sign offered advantages compared with LEDs located within or below the sign. To determine if the position of the beacons affected driver yielding, RRFBs were installed above and below the pedestrian crossing sign at 13 sites in four locales. A staged pedestrian protocol was used to collect driver yielding to ensure a consistent presentation of approaching pedestrians. Preliminary findings showed only minor, if any, differences between the above and below positions (average daytime yielding for staged pedestrians was 64% for above and 61% for below), and the statistical test showed no significant difference. The open-road study found that the position of the RRFB did not affect a driver’s decision to yield. With apparent benefits identified from the closed-course study—i.e., lower discomfort and improved ability to detect the pedestrian as measured by identifying the direction a cutout photo of a pedestrian is traveling—and the lack of difference in driver yielding as a result of position, locating the beacons above the warning sign could improve the overall effectiveness of this treatment. As a result of these findings, FHWA plans to issue an official interpretation permitting placement of the beacons above the crossing warning sign.

Distraction has been a point of interest in transportation research for many years. Recently, this interest has extended from distracted drivers to distracted pedestrians. Past research suggests that distracted pedestrians are less likely to show cautionary crossing habits and tend toward increased crossing times. This study provided information about the pedestrian waiting to cross and investigated how distraction and other factors may have affected pedestrian start-up time and crossing behaviors. Researchers surreptitiously observed 760 pedestrians at three intersections in College Station, Texas, and coded their characteristics and behavior in real time. Characteristics recorded were age, gender, distraction, and grouping. Distractions recorded were talking on a phone, texting, listening to music, eating, drinking, smoking, and other. The pedestrian groups were no group (crossed alone), mixed-age group, and peer group. Behaviors recorded were glancing before entering the crosswalk, entering the crosswalk early, walking within the crosswalk markings, and hurrying across the crosswalk. Pedestrians who texted and pedestrians who talked on a phone had 21% and 31% more start-up time, respectively. Additionally, pedestrians in mixed-age groups had 14% more start-up time. Texting pedestrians were about two times less likely to glance before entering the crosswalk compared with undistracted pedestrians. Similarly, a pedestrian engaged in a phone conversation was about five times less likely to glance. These results may provide insight into ongoing discussion on how to address distracted pedestrians crossing the street.

The pedestrian hybrid beacon (PHB) has shown great potential in improving safety and driver yielding; however, questions have been asked about actual driver and pedestrian behavior. A data set reflecting more than 78 h of video data recorded at 20 locations included 1,979 pedestrians crossing during 1,149 PHB actuations. For the 20 sites, driver yielding to pedestrians averaged 96%. For the majority of the pedestrians who left during the dark indication (124 of 1,979, which was 6%), the roadway volume was such that the pedestrian was able to find sufficient gaps (fewer than four vehicles/min/lane for the majority of these crossings). Overall, 91% of the pedestrians pushed the pushbutton. A greater number of pedestrians activated the device on a road with a posted speed limit of 45 mph compared with roads with a posted speed limit of 40 mph or less. When the equivalent hourly volume was 1,500 vehicles/h or more, the percentage of pedestrians activating the PHB was always 92% or more. The conflict rate was found to be higher for noncompliant pedestrians than for compliant pedestrians. More conflicts occurred at locations with nearby bus stops or driveways.

Several methods have been used to emphasize the presence of a pedestrian crossing, including supplementing signing with beacons. A device that has received national attention is the rectangular rapid-flashing beacon (RRFB). A question being asked is whether the position of the beacons above or below the pedestrian crossing sign influences the effectiveness of the treatment. A closed-course study found that at night RRFBs located above the crossing sign offered advantages compared with LEDs located within or below the sign. To determine if the position of the beacons affected driver yielding, RRFBs were installed above and below the pedestrian crossing sign at 13 sites in four locales. A staged pedestrian protocol was used to collect driver yielding to ensure a consistent presentation of approaching pedestrians. Preliminary findings showed only minor, if any, differences between the above and below positions (average daytime yielding for staged pedestrians was 64% for above and 61% for below), and the statistical test showed no significant difference. The open-road study found that the position of the RRFB did not affect a driver’s decision to yield. With apparent benefits identified from the closed-course study—i.e., lower discomfort and improved ability to detect the pedestrian as measured by identifying the direction a cutout photo of a pedestrian is traveling—and the lack of difference in driver yielding as a result of position, locating the beacons above the warning sign could improve the overall effectiveness of this treatment. As a result of these findings, FHWA plans to issue an official interpretation permitting placement of the beacons above the crossing warning sign.

This research effort identified the operational and safety implications of the use of reduced lane and shoulder widths for a variety of urban freeway configurations. The study used speed, crash, and geometric data for freeways in Dallas, Houston, and San Antonio, Texas. The operational analysis identified an increase of about 2.2 mph in speed for a 12-ft lane compared with an 11-ft lane. The shoulder width is significant when the adjacent lane is 11 ft wide, but not when it is 12 ft wide. These findings suggest that the width of the left shoulder is more important with a reduced lane width. Operating speeds on Texas freeways are 2 mph lower during nighttime (with roadside lighting present) than during the day. Speeds were higher (by 1.5 mph) on the weekends (Saturday) than on the weekday studied (Wednesday). The safety analysis determined a crash difference when freeways with 12- to 11-ft lanes were compared. There was a reduction in fatal and injury crashes that ranged from 5% for two-lane freeways up to 12% for five-lane freeways. Similarly, some crash reductions were associated with each additional lane, increased left shoulder widths, and increased right shoulder widths. This paper concludes with a series of sample problem scenarios that collectively demonstrate how the resulting operating speed and crash prediction models allow practitioners to assess the trade-offs that can be expected when urban freeway lane and shoulder widths are modified.

As part of a recent research project on countermeasures for pedestrian crashes in Texas, researchers conducted a before-and-after field study to identify changes in driver yielding and selected pedestrian behaviors that resulted from the installation of rectangular rapid-flashing beacons at four sites and a pedestrian hybrid beacon at one site at previously untreated crosswalks. The installations resulted in noticeable improvement in the proportion of yielding vehicles, with increases of 35 to 80 percentage points at the study sites. Most (94%) of the nonstaged pedestrians activated the treatment at treated sites. An increase in the number of nonstaged pedestrian crossings was observed after the pedestrian hybrid beacon was installed at the study site. Nearside yielding rates were higher for nonstaged pedestrians who waited at the edge of the travel lane than for those who waited at the top of the curb ramp. Pedestrian searching behavior for crossings not controlled by a crossing guard was common, with 92% of pedestrians looking at least in one direction and 68% looking in both directions at least once.

Several methods, including one that supplements signage with beacons or embedded LEDs, have been used to emphasize the presence of a pedestrian crossing. A device that has received national attention is the rectangular rapid-flashing beacon (RRFB). A question that is being asked about the device is whether the beacons need to be rectangular. Could they be circular? For a comparison of the two devices, RRFBs and circular rapid-flashing beacons (CRFBs) were installed at 12 sites in four cities (i.e., Milwaukee, Wisconsin; Flagstaff, Arizona; Austin, Texas; and College Station, Texas). CRFBs were installed initially at half of the sites, while RRFBs were installed at the other half. The same flash pattern was used in all cases, regardless of beacon shape. A staged pedestrian protocol was used to collect driver yielding data to ensure that oncoming drivers received a consistent presentation of approaching pedestrians. The preliminary findings showed only minor, if any, differences between the CRFB and the RRFB (i.e., average daytime yielding rate with CRFB was 63%; it was 59% with RRFB). The results from the generalized linear mixed model indicated no significant differences between the two beacon shapes (p-value = .4717). For a subset of the sites, the luminous intensity (also called brightness) of the beacons was measured. There was evidence of an increasing yielding rate with increasing intensity at night. In conclusion, the shape of the yellow rapid-flashing beacon did not have an impact on whether a driver decided to yield to waiting pedestrians.

Several methods have been used to emphasize the presence of a pedestrian crossing, including one that supplements signage with beacons or embedded LEDs. Rapidly flashing beacons constitute one type of treatment used at midblock pedestrian crossings to bring drivers’ attention to a crossing pedestrian. This study evaluated the effect of the activation of the beacon and traffic volumes on driver yielding behavior when a crossing pedestrian was present. Rectangular rapid-flashing beacons (RRFBs) and circular rapid-flashing beacons (CRFBs) were installed at 12 sites in four cities. At approximately half of the study sites, RRFBs were initially installed and later replaced with CRFBs. At the other study sites, CRFBs were initially installed and later replaced with RRFBs. The same flash pattern was used for both beacon shapes. Driver yielding rates were compared between pedestrian crossings when a beacon was activated and when it was not. The results of the analysis showed that when a beacon, whether rectangular or circular, was activated, a driver was 3.68 times more likely to yield to pedestrians than when the beacon was not activated. The results of an analysis of the relationship between traffic volume and driver yielding indicated that driver yielding behavior was not influenced by traffic volume at the study sites.

Research has shown that rapid-flashing beacons (RFBs) at marked pedestrian crossings increase driver yielding rates at these locations. There are recommended minimum intensity levels for these devices, but no guidelines exist for maximum intensity levels that would cause light glare to drivers at night. This paper searches for evidence of such maximum thresholds by analyzing two data sets. One data set represented driver yielding at various RFB intensity levels; the data were collected from four cities in Arizona, Wisconsin, and Texas. The other data set was from a human factors study conducted on a closed course. These data were collected from volunteers in Texas who were asked to indicate their discomfort glare rating of various beacon intensities at a simulated pedestrian crossing. On the basis of the data set containing driver yielding rates, researchers estimated a minimum nighttime intensity of 1,100 candela (cd) was needed for the expected yielding rate at night to be at least the same as the yielding rate during the day. The wide dispersion of yielding rates in this data set made it impractical to find a minimum intensity in a more general way. More research is needed to reach a better explanation of the wide range of yielding rates. On the basis of the second data set, it was determined that driver discomfort from glare may become an issue at an intensity of approximately 1,000 cd. It is estimated that a maximum intensity of 1,350 cd at night should keep drivers’ ratings of glare as being “unbearable” to 15% at most.

As part of a recent research project on countermeasures for pedestrian crashes in Texas, researchers conducted a before-and-after field study to identify changes in driver yielding and selected pedestrian behaviors that resulted from the installation of rectangular rapid-flashing beacons at four sites and a pedestrian hybrid beacon at one site at previously untreated crosswalks. The installations resulted in noticeable improvement in the proportion of yielding vehicles, with increases of 35 to 80 percentage points at the study sites. Most (94%) of the nonstaged pedestrians activated the treatment at treated sites. An increase in the number of nonstaged pedestrian crossings was observed after the pedestrian hybrid beacon was installed at the study site. Nearside yielding rates were higher for nonstaged pedestrians who waited at the edge of the travel lane than for those who waited at the top of the curb ramp. Pedestrian searching behavior for crossings not controlled by a crossing guard was common, with 92% of pedestrians looking at least in one direction and 68% looking in both directions at least once.

Several methods, including one that supplements signage with beacons or embedded LEDs, have been used to emphasize the presence of a pedestrian crossing. A device that has received national attention is the rectangular rapid-flashing beacon (RRFB). A question that is being asked about the device is whether the beacons need to be rectangular. Could they be circular? For a comparison of the two devices, RRFBs and circular rapid-flashing beacons (CRFBs) were installed at 12 sites in four cities (i.e., Milwaukee, Wisconsin; Flagstaff, Arizona; Austin, Texas; and College Station, Texas). CRFBs were installed initially at half of the sites, while RRFBs were installed at the other half. The same flash pattern was used in all cases, regardless of beacon shape. A staged pedestrian protocol was used to collect driver yielding data to ensure that oncoming drivers received a consistent presentation of approaching pedestrians. The preliminary findings showed only minor, if any, differences between the CRFB and the RRFB (i.e., average daytime yielding rate with CRFB was 63%; it was 59% with RRFB). The results from the generalized linear mixed model indicated no significant differences between the two beacon shapes (p-value = .4717). For a subset of the sites, the luminous intensity (also called brightness) of the beacons was measured. There was evidence of an increasing yielding rate with increasing intensity at night. In conclusion, the shape of the yellow rapid-flashing beacon did not have an impact on whether a driver decided to yield to waiting pedestrians.

Several methods have been used to emphasize the presence of a pedestrian crossing, including one that supplements signage with beacons or embedded LEDs. Rapidly flashing beacons constitute one type of treatment used at midblock pedestrian crossings to bring drivers’ attention to a crossing pedestrian. This study evaluated the effect of the activation of the beacon and traffic volumes on driver yielding behavior when a crossing pedestrian was present. Rectangular rapid-flashing beacons (RRFBs) and circular rapid-flashing beacons (CRFBs) were installed at 12 sites in four cities. At approximately half of the study sites, RRFBs were initially installed and later replaced with CRFBs. At the other study sites, CRFBs were initially installed and later replaced with RRFBs. The same flash pattern was used for both beacon shapes. Driver yielding rates were compared between pedestrian crossings when a beacon was activated and when it was not. The results of the analysis showed that when a beacon, whether rectangular or circular, was activated, a driver was 3.68 times more likely to yield to pedestrians than when the beacon was not activated. The results of an analysis of the relationship between traffic volume and driver yielding indicated that driver yielding behavior was not influenced by traffic volume at the study sites.

Research has shown that rapid-flashing beacons (RFBs) at marked pedestrian crossings increase driver yielding rates at these locations. There are recommended minimum intensity levels for these devices, but no guidelines exist for maximum intensity levels that would cause light glare to drivers at night. This paper searches for evidence of such maximum thresholds by analyzing two data sets. One data set represented driver yielding at various RFB intensity levels; the data were collected from four cities in Arizona, Wisconsin, and Texas. The other data set was from a human factors study conducted on a closed course. These data were collected from volunteers in Texas who were asked to indicate their discomfort glare rating of various beacon intensities at a simulated pedestrian crossing. On the basis of the data set containing driver yielding rates, researchers estimated a minimum nighttime intensity of 1,100 candela (cd) was needed for the expected yielding rate at night to be at least the same as the yielding rate during the day. The wide dispersion of yielding rates in this data set made it impractical to find a minimum intensity in a more general way. More research is needed to reach a better explanation of the wide range of yielding rates. On the basis of the second data set, it was determined that driver discomfort from glare may become an issue at an intensity of approximately 1,000 cd. It is estimated that a maximum intensity of 1,350 cd at night should keep drivers' ratings of glare as being “unbearable” to 15% at most.

This study evaluated the effect of yellow rapid flashing beacon characteristics on the ability to detect objects located behind a sign during a closed-course driving study sponsored by FHWA. For the analysis focusing on object detection distance, the results indicated that certain study assemblies were associated with shorter object detection distances. During the day, the object detection distance was shorter for objects behind an assembly with two rectangular beacons below the sign (R-B), as opposed to other beacon arrangements, such as two rectangular beacons above the sign and two circular beacons below or above the sign. At night, the detection distance to an object was shorter behind an assembly with R-B when compared with an assembly with two 12-in. circular beacons below the sign. These findings indicated that characteristics of the R-B, such as the light intensity or the location of the beacons, might negatively affect the driver's ability to see an object. For the analysis focusing on the accuracy of detecting objects, which considered the number of objects missed by the participants, the location of the beacons (above or below the sign) was significant during the day but not at night. During the day, participants were less likely to miss an object when the beacons were above the sign.

This research effort explored the factors associated with higher driver yielding rates at pedestrian crossings with traffic control signal (TCS), pedestrian hybrid beacon (PHB), and rectangular rapid-flashing beacon (RRFB) treatments in Texas. The percentages of drivers yielding to a staged pedestrian were collected at 7 TCS sites, 22 RRFB sites, and 32 PHB sites. Overall, TCSs in Texas had the highest driver yielding rates, with an average of 98%. The average driver yielding rate for RRFBs in Texas was 86%, whereas the average for PHBs was 89%. The RRFB results for Texas were slightly higher than those found in other studies, perhaps because all RRFB sites included in this analysis had "School Crossing" signs and were located near a school. The number of devices within a city may have an impact on driver yielding. Those cities with a greater number of a particular device (i.e., Austin, Texas, for the PHBs and Garland, Texas, for the RRFBs) had higher driver yielding rates than cities where the device was used at only a few crossings. A comparison of the number of days since installation revealed statistically significantly higher driver yielding rates for those devices that had been installed longer. For PHBs, the results support the use of PHBs on roadways with multiple lanes or a wide crossing. For RRFBs, a lower rate of compliance was observed for longer crossing distances and indicated that for a certain crossing distance width, a device other than the RRFB should be considered.

The goal of this research was to determine the effects of geometric characteristics on double left-turn lane (DLTL) operations, as measured with saturation flow rate (SFR) in units of passenger cars per hour of green per lane (pcphgpl). Data from 26 sites located in three states (Arizona, California, and Texas) were used in the analyses. The average DLTL SFR was 1,775 pcphgpl. The inside-outside lane variable was found to be not significant, which means that the SFRs of the inside and outside lanes are similar. For each additional U-turning vehicle in the left-turn queue, SFR would decrease by 56 pcphgpl after accounting for the effects of other variables in the model. The model results indicate that the addition of a new lane on the receiving leg from a channelized right turn resulted in an SFR increase of about 50 pcphgpl. Width of the left-turn lanes did not significantly affect the SFR. The SFR determination method requires elimination of a queue if a heavy vehicle is present. Therefore, even though the operations of queues with only passenger cars are similar for the various left-turn lane widths studied (9.5 to 13 ft), results for the operations of queues that include heavy vehicles (i.e., trucks or buses) may be different. The width of the receiving leg represents the visual target for left-turning drivers. When the receiving leg width was between 24 and 36 ft, the average SFR was 1,725 pcphgpl, whereas a receiving leg width of 40 to 54 ft was associated with an average SFR of 1,833 pcphgpl. One potential change to practice on the basis of this research is to modify guidance documents to reflect the finding that the capacity of DLTLs is approximately 196% of a single median lane rather than 180%.

This study evaluated the effect of yellow rapid flashing beacon characteristics on the ability to detect objects located behind a sign during a closed-course driving study sponsored by FHWA. For the analysis focusing on object detection distance, the results indicated that certain study assemblies were associated with shorter object detection distances. During the day, the object detection distance was shorter for objects behind an assembly with two rectangular beacons below the sign (R-B), as opposed to other beacon arrangements, such as two rectangular beacons above the sign and two circular beacons below or above the sign. At night, the detection distance to an object was shorter behind an assembly with R-B when compared with an assembly with two 12-in. circular beacons below the sign. These findings indicated that characteristics of the R-B, such as the light intensity or the location of the beacons, might negatively affect the driver's ability to see an object. For the analysis focusing on the accuracy of detecting objects, which considered the number of objects missed by the participants, the location of the beacons (above or below the sign) was significant during the day but not at night. During the day, participants were less likely to miss an object when the beacons were above the sign.

This research effort explored the factors associated with higher driver yielding rates at pedestrian crossings with traffic control signal (TCS), pedestrian hybrid beacon (PHB), and rectangular rapid-flashing beacon (RRFB) treatments in Texas. The percentages of drivers yielding to a staged pedestrian were collected at 7 TCS sites, 22 RRFB sites, and 32 PHB sites. Overall, TCSs in Texas had the highest driver yielding rates, with an average of 98%. The average driver yielding rate for RRFBs in Texas was 86%, whereas the average for PHBs was 89%. The RRFB results for Texas were slightly higher than those found in other studies, perhaps because all RRFB sites included in this analysis had “School Crossing” signs and were located near a school. The number of devices within a city may have an impact on driver yielding. Those cities with a greater number of a particular device (i.e., Austin, Texas, for the PHBs and Garland, Texas, for the RRFBs) had higher driver yielding rates than cities where the device was used at only a few crossings. A comparison of the number of days since installation revealed statistically significantly higher driver yielding rates for those devices that had been installed longer. For PHBs, the results support the use of PHBs on roadways with multiple lanes or a wide crossing. For RRFBs, a lower rate of compliance was observed for longer crossing distances and indicated that for a certain crossing distance width, a device other than the RRFB should be considered.

The goal of this research was to determine the effects of geometric characteristics on double left-turn lane (DLTL) operations, as measured with saturation flow rate (SFR) in units of passenger cars per hour of green per lane (pcphgpl). Data from 26 sites located in three states (Arizona, California, and Texas) were used in the analyses. The average DLTL SFR was 1,775 pcphgpl. The inside–outside lane variable was found to be not significant, which means that the SFRs of the inside and outside lanes are similar. For each additional U-turning vehicle in the left-turn queue, SFR would decrease by 56 pcphgpl after accounting for the effects of other variables in the model. The model results indicate that the addition of a new lane on the receiving leg from a channelized right turn resulted in an SFR increase of about 50 pcphgpl. Width of the left-turn lanes did not significantly affect the SFR. The SFR determination method requires elimination of a queue if a heavy vehicle is present. Therefore, even though the operations of queues with only passenger cars are similar for the various left-turn lane widths studied (9.5 to 13 ft), results for the operations of queues that include heavy vehicles (i.e., trucks or buses) may be different. The width of the receiving leg represents the visual target for left-turning drivers. When the receiving leg width was between 24 and 36 ft, the average SFR was 1,725 pcphgpl, whereas a receiving leg width of 40 to 54 ft was associated with an average SFR of 1,833 pcphgpl. One potential change to practice on the basis of this research is to modify guidance documents to reflect the finding that the capacity of DLTLs is approximately 196% of a single median lane rather than 180%.

Because complexity typically is a qualitative characteristic, the ability to evaluate the complexity of an interchange objectively is somewhat difficult. This difficulty is compounded when trying to compare the complex features of multiple interchanges. A spreadsheet-based decision tool that was developed as a method for the quantification and comparison of the complexity of freeway interchanges in the United States is discussed. The initial discussion focuses on the steps that guided researchers in the development of the spreadsheet, and this discussion is followed by a description of the spreadsheet itself and how practitioners can use it to evaluate the complexity of interchanges under their consideration. A review is provided of the results researchers obtained with the spreadsheet in an evaluation of the complexity of 28 existing interchanges in 11 states. These study sites ranged from relatively simple to complex, and results indicated that the spreadsheet-generated scores were generally consistent with researchers' qualitative estimates of the sites' relative complexity. The meaning and interpretation of the spreadsheet results are discussed.

Because complexity typically is a qualitative characteristic, the ability to evaluate the complexity of an interchange objectively is somewhat difficult. This difficulty is compounded when trying to compare the complex features of multiple interchanges. A spreadsheet-based decision tool that was developed as a method for the quantification and comparison of the complexity of freeway interchanges in the United States is discussed. The initial discussion focuses on the steps that guided researchers in the development of the spreadsheet, and this discussion is followed by a description of the spreadsheet itself and how practitioners can use it to evaluate the complexity of interchanges under their consideration. A review is provided of the results researchers obtained with the spreadsheet in an evaluation of the complexity of 28 existing interchanges in 11 states. These study sites ranged from relatively simple to complex, and results indicated that the spreadsheet-generated scores were generally consistent with researchers’ qualitative estimates of the sites’ relative complexity. The meaning and interpretation of the spreadsheet results are discussed.

Left-turn movements at intersections, including driveways—especially movements that are made from lanes that are shared with through traffic—cause delays and adversely affect safety. Although some left-turn warrants have been updated, many agencies still use research performed by M. D. Harmelink in the mid-1960s. Most states use procedures that are based on Harmelink's work, but several limitations have been identified. Economic analysis can provide a useful method for combining traffic operations and safety benefits of left-turn lanes to identify situations in which left-turn lanes either are or are not justified economically. This project used a benefit-cost approach to determine when a left-turn lane would be justified. The steps included simulation to determine delay savings from installing a left-turn lane, crash costs and crash reduction savings determined from safety performance functions and crash modification factors available in the Highway Safety Manual, and construction costs. Left-turn lane warrants were developed for rural two-lane highways, rural four-lane highways, and urban and suburban roadways. In addition, warrants for bypass lanes were developed for rural two-lane highways.

As traffic volumes increase in both urban and rural areas, so do demands on the highway network. Specifically, as rural traffic volumes rise in Texas, the pressure on the state's network of two-lane highways rises accordingly. Previous research in Texas demonstrated that periodic passing lanes can improve operations on two-lane highways with average daily traffic lower than 5,000 vehicles. These highways, called Super 2 highways, can provide many of the benefits of a four-lane alignment at a lower cost. A recent project expanded on that research to develop design guidelines for passing lanes on two-lane highways with higher volumes. Researchers investigated the effects of volume, terrain, and heavy vehicles on traffic flow and safety. This paper discusses findings from field observations and crash analysis of existing Super 2 highway corridors in Texas and computer modeling of traffic conditions on a simulated Super 2 corridor. Results indicate that passing lanes provide added benefit at higher traffic volumes by reducing crashes, delay, and percent time spent following. Empirical Bayes analysis of crash data reveals a 35% reduction in expected nonintersection crashes with injuries. Simulation results indicate that most passing activity takes place within the first mile of the passing lane, so additional passing lanes can offer greater benefit than longer passing lanes. Whether new passing lanes are added or existing lanes are lengthened, the incremental benefit diminishes as additional length is provided and the highway more closely resembles a four-lane alignment.

This study evaluated high-beam usage on low-volume roadways in Texas. Most previous studies used a subjective approach to determine high-beam usage that involved a stationary observer or an observer driving around the study section. For more efficient data collection, this study used photometric readings as the methodology. This approach allowed for a quantitative measure of high-beam use, in that it did not rely on an observer's opinion as to whether the headlamps were on high or low beam. Preliminary data collection was conducted as part of the study to estimate the threshold high-beam illuminance value; these illuminance data showed moderate use of high beams on low-volume, rural two-lane highways, with 42% of the free-flow drivers using high beams. There was a wide variation in high-beam use between sites, so site characteristics were reviewed to identify potential reasons for this variation. The data were fit to a logistic regression model to estimate the impact of various site characteristics on a driver's decision to use high beams. The results showed that vehicle speed, paved surface width, number of access points within 1,000 ft of the site, and presence of horizontal curves within 1 mi of the site were statistically significant factors that contributed to the probability of high-beam use. The results also showed that higher vehicle speeds, narrow paved surfaces, presence of horizontal curves, and few or no access points led to a higher probability of highbeam use. These results are intuitive and support the observations made in the exploratory data analysis.

The objective of this study was to evaluate the safety effectiveness of Super 2 highways in Texas. A before-after study was performed with the empirical Bayes (EB) method, which was superior to other methods because it could address the regression-to-the-mean bias. On the basis of potential study sites identified in seven districts (Paris, Childress, Corpus Christi, Austin, Wichita Falls, Yoakum, and Bryan) in Texas, four reference groups were considered by imposition of different restrictions. Negative binomial regression models were then used to develop safety performance functions for each reference group. From the model selection process, the most restricted reference group was selected for the final analysis. For roadway inventory and crash history data, 12 years (1997 to 2001 and 2003 to 2009) of data for Texas were examined. The analysis used fatal (K), incapacitating injury (A), nonincapacitating injury (B), and minor injury (C) crashes. Property-damage-only crashes were not included. The EB analyses were carried out on five corridors with about 53 centerline miles. The results showed that the installation of Super 2 highways led to statistically significant reductions in the incidence of crashes of 35% for crashes on segments only (KABC) and 42% for crashes on segments and at intersections (KABC) on the study corridors. These findings were consistent with those of previous studies of the safety of Super 2 corridors that showed improvements in safety with installation of passing lanes, even when traffic volumes were higher than those considered under previous guidance in Texas.