Tomas Lindheimer

Comparison of Above-Sign and Below-Sign Placement of Rectangular Rapid-Flashing Beacons

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.

Operating Speed on a Buffer-Separated Managed Lane

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.

Methods for Estimating Axle Factors and Axle Classes from Vehicle Length Data

This study developed methods to estimate axle factors and vehicle class from length-based data streams. A set of eight methods was proposed and evaluated in different testing schemes intended to observe performance on homogeneous and heterogeneous data. The initial analysis used length-based data from 61 sites in Wisconsin. The research team compared performance of the methods estimating axle factors and vehicle class proportions. Performance was comparable and consistent between homogeneous and heterogeneous subsets of data. The research team selected two methods for a final round of analysis based on their accuracy and robustness to heterogeneity. For the final round of analysis, the research team assembled a multistate dataset using data from Wisconsin and from 14 other states represented in a dataset from the Long Term Pavement Performance program. The final round of analysis compared performance under different seasons, facility type, and road character (urban vs. rural). Performance of the two identified methods was deemed appropriate and they are recommended for implementation.

Closed Course Performance Testing of a Work Zone Intrusion Alarm System

Oldcastle Materials, Inc. and ARTIS, LLC joined forces to develop an innovative work zone intrusion detection and alarm system. The alarm system flashes light-emitting diodes and emits an audible alarm if an intrusion is detected. Texas A&M Transportation Institute performed a closed course study to assess performance of the alarm system under conditions that may occur in real work zones. This testing was intended to verify that the alarm system does produce the proper alert when conditions warrant it and that alerts were not activated when conditions did not warrant them (i.e., that the system does not produce false alarms). Performance of the worker body alarms (designed to be worn by field personnel and activated when an intrusion threat is detected) was also evaluated. During testing, these devices were positioned at various locations to assess the ability of the system to correctly determine the location of the devices and their position relative to the intrusion threat. The alarm system was tested under two operating modes: lane closures and flagging operations. Several approach vehicle trajectories were used in both operating modes. The main alarm achieved a 100% success rate, whereas the worker body alarms achieved a 97% success rate. Unsuccessful events for the worker body alarms were attributable to the test protocol exceeding the effective communication range of the intrusion detection system. Ongoing improvements in the device are expected to significantly increase this communication range. All other device locations, scenarios, and trajectories tested achieved a 100% success rate.

Effect of Geometric Factors on Lateral Position of Vehicles in Freeway Buffer-Separated Managed 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).

Evaluation of Confirmation Lights on Red Light Running Violations by Time-into-Red Phase

Red light running (RLR) crashes at urban signalized intersections continue to be a serious safety concern for many communities across the United States. Recent national crash data indicated that 676 fatalities were caused by RLR in 2009, which represents approximately 10% of all intersection crashes and 2% of all roadway fatalities. This research studied confirmation lights and their effect on RLR violations’ time into red. Two sets of confirmation lights were installed at two busy urban intersections in Overland Park, Kansas. With the use of a binomial test of proportions, the study found that there was a significant increase in violations within the first second of the red indication 1 month after deployment. Three months after deployment, there was a decrease in violations over 1 s, but this decrease was statistically not significant. Although there was an observed increase in violation rate, the increase did not translate into violations occurring later in the red cycle. In the 3-month after-period, there was a decrease in the violation rate but an increase in violations within the first second of the red indication and a decrease in violations between 1.0 and 3.0 s. The results for this period were statistically not significant and which suggest that the confirmation light had little effect on a violation’s time into the red. In all periods after deployment, there were no violations occurring after 3 s into the red. This finding means that drivers did not use the confirmation lights to traverse the intersection during the all-red cycle.

Value of confirmation lights and their unintended impact on driver compliance and deterrence to running a red light

In the United States, red light running (RLR) continues to be a safety concern for many communities with signalized intersections. In 2012, the Insurance Institute for Highway Safety reported that nationwide, RLR had resulted in 683 fatalities and 133,000 injury-related crashes. Confirmation lights have been deployed in many communities as a countermeasure to aid law enforcement in reducing RLR violations; however, the effectiveness of confirmation lights has not been well documented. This research study was conducted to determine the effectiveness of confirmation lights at signalized intersections for the purpose of reducing RLR violations. Confirmation lights were installed for the protected left-turn movements at two signalized intersections in Lawrence, Kansas. In addition to the two treatment sites, 11 comparison sites, including six spillover intersections and five control intersections, were studied. A before–after analysis was conducted with field-based violation data. Without changing the local, traditional police department–run RLR enforcement program during the study period, video data were collected before installation, and 1 month and 3 months after installation. A test of proportions found a statistically significant 42% reduction in left-turning RLR violations 3 months after the installation of confirmation lights at the treatment sites. An analysis of RLR time into red with chi-square tests indicated that the system was less effective in changing the time from the onset of red until the mean RLR violation occurred. Overall, the presence of the confirmation lights at the signalized intersection indicated effectiveness in both reducing the number of RLR violations and also changing driver behavior.