Pay Attention!

Safety Article June 11, 2009
Printer-friendly version

Visitors to downtown Houston have probably seen the Metropolitan Transit Authority of Harris County’s (Metro) Red Line. It is a 7.5-mile stretch of light-rail transit (LRT) that links the central business district with Midtown, the Museum District, the Texas Medical Center and Reliant Park.

What visitors might not have noticed is how some motorists seem to ignore vehicle-train safety.

A number of crashes have occurred on the Red Line involving passenger and light-rail vehicles, with one crash resulting in a fatality. Initially, this was a three-year evaluation designed to test technologies that supplement standard traffic-control devices at the LRT crossings. The goal is to reduce the kinds of driver behavior that may lead to crashes. If additional devices can help drivers pay better attention to what the signals, signs and pavement markings are already telling them, Metro can help keep drivers, pedestrians and transit riders safer.

In 2004, the first 7.5 miles of MetroRail (the Red Line) was constructed by Metro to fulfill part of the long-range transportation plan for Houston. This light-rail line travels at grade along surface streets, to the left or right of the vehicle travel lanes in some areas and in the street median in others. After the Red Line was opened, Metro noticed a large number of crashes along the Red Line involving both a passenger motor vehicle and a light-rail vehicle (LRV).

Some of these crashes involved a vehicle running a red light on the cross street that intersects both the rail line and the parallel arterial street, and one of the crashes resulted in a fatality. It was unclear what the primary causes of these types of crashes were, but driver inattention or issues with visual clutter were surmised as primary causative factors.

In order to reduce red-light running, right-turn-on-red violations and crashes at these intersections, Metro installed two innovative traffic-control devices: a lighted stop-bar system (LSBS) and a light-emitting diode (LED) outlined traffic-signal backplate. Each of these treatments was installed with the approval of the Federal Highway Administration through the experimentation request process.

Belly up to the stop bar

In response to the crashes, Metro outfitted the stop bar at the Jefferson Street approach to Main Street with an LSBS to enhance visibility of the red interval indications at the signalized intersection. The LSBS was installed in the pavement, preceding the painted stop bar for the eastbound Jefferson Street approach to Main Street. Jefferson Street is a five-lane, one-way eastbound street that intersects the MetroRail line, which runs in the center of Main Street.

Prior to the installation of the LSBS, there were two traffic-signal heads on the far side of the intersection. In addition to pedestrian signal heads on both sides of Jefferson, there also were three different signs on the near side of the intersection and one sign on the far side. On the near side, the signs were: a divided highway with a light-rail transit crossing sign (R15-7), a no-right-turn-on-red sign (R10-11T) and a highway-rail grade crossing advance warning sign (W10-1). On the far side of the intersection, there was a no-right-turn-on-red sign. Right turns on red are prohibited on the Jefferson Street approach to the intersection, and on any cross-street approach to Main Street in downtown Houston. All of these traffic-control devices were in place before the LSBS was installed, and they remained in place after the installation.

The LSBS evaluated at this location was configured in a linear layout with two offset rows of red LED markers installed in front of the painted stop line. The spacing of individual markers in each row was approximately 1 ft, but the offset of the markers between the two rows effectively presents 6-in. spacing. The LSBS was activated on March 25, 2006, and operates in a steady-burn mode with red-lighted pavement markers active when the eastbound traffic-signal indication for Jefferson Street approach displays the red indication. During the green interval and yellow change interval, these pavement markers are off and inconspicuous. Further, the LSBS is deactivated when the traffic signal operates in an all-red flashing mode.

The anticipated impact of this countermeasure was to increase driver awareness to the traffic signal and red indication, reducing red-light running and right-turn-on-red violations.

Get the LED out

Metro also installed the LED-outlined traffic-signal backplates at an intersection in downtown Houston with the hope that they would help increase the visibility of the traffic-signal face assembly and reduce red-light running violations and crashes. The LED-outlined traffic-signal backplates were installed on each of the two signal heads for the westbound Gray Street approach to Main Street in downtown Houston.

The backplates were activated on Oct. 13, 2006, and they are operated in a steady-burn mode with an LED light source producing a continuous line of red light around the outer border of the traffic-signal backplate for each of the two traffic-signal heads on that approach. The red backplate outline is activated at the onset of the red indication and remains active for the duration of the red interval, producing a red-box outline around the traffic-signal head. During the green interval and yellow change interval, the red outline of the backplate is off and inconspicuous.

The anticipated impact of this countermeasure was to increase driver awareness to the traffic signal and onset of red indication. The anticipated benefit was a reduction in red-light running.

Condition red

Each year, red-light-running crashes result in numerous injuries and deaths. For example, there were 171,000 crashes, 144,000 injuries and 887 fatalities attributed to red-light running in the U.S. during 2006. In order to reduce the number of red-light-running crashes, agencies may apply a variety of countermeasures.

Enforcement countermeasures can include police enforcement (typically consisting of having a police officer stationed near the intersection to detect, follow and stop violators) or camera enforcement.

Red-light camera enforcement has received much attention in recent years, partly because of their increased use across the U.S. As of July 2008, over 300 communities are using red-light cameras in 25 states and the District of Columbia. However, detractors often claim that the goal of red-light cameras is to make money from violators, rather than to deter or prevent drivers from running red lights. Also, some legal issues have prevented red-light cameras from being used in certain places. In order for cameras to be used for law enforcement, state legislation or, in some cases, local legislation must make it legal for enforcement agencies to send citations to red-light violators by mail. As a result, red-light camera enforcement is currently authorized in about half of the states.

Engineering countermeasures can include various improvements. They can be categorized into three groups of countermeasures: signal operation, motorist information and physical improvement. Signal operation countermeasures include modifying phasing, cycle length or change intervals. Motorist information countermeasures might include providing advance information to drivers or improving driver notification. Physical improvement typically involves safety or operational improvements like adding capacity or reducing the magnitude of vertical or horizontal curves.

Lighted pavement markers are currently used for a variety of roadway applications. Specifically, they can be used in four general types of applications: to warn, to guide, to regulate or to provide illumination. Currently, lighted pavement markers are mentioned in the Manual on Uniform Traffic Control Devices (MUTCD) under section 4L.02 “In-Roadway Warning Lights at Crosswalks.” According to the MUTCD, these in-roadway lights are considered a type of traffic signal and not pavement markers, and they must be installed at marked crosswalks while displaying a flashing-yellow-signal indication, among other listed requirements.

Besides in-roadway lights at crosswalks, no other application of lighted pavement markers are currently included in the MUTCD. Some other applications include the following: warning at highway-rail crossings and on horizontal curves; guidance for multiple turn lanes, merge locations and tunnels; regulation at intersection stop bars and for left-turn restrictions; and illumination at vehicle inspection points.

The use of lighted pavement markers for illuminated stop lines has been fairly limited; however, a few applications have been installed in recent years. In 1999, the city of Anaheim, Calif., installed LED lights across the northbound and southbound stop lines at an intersection that had high levels of red-light running. These markers displayed a flashing yellow during the yellow change interval of the northbound and southbound traffic signal. During the red traffic-signal indication, the lighted pavement markers displayed a steady red. These lighted stop lines were credited with reducing red-light-running violations from 8.94 per 1,000 vehicles to 2.40 violations per 1,000 vehicles during a before-and-after study.

In 2003, the Uptown Development Authority in Houston installed a similar lighted stop-line system at a signalized pedestrian crossing intersection near the Galleria mall. A before-and-after study showed reductions in red-light-running violations as well as increased pedestrian compliance following the implementation of the lighted stop line.

One way to reduce red-light running is to increase motorist information with regard to the traffic signal. Some of these possible improvements include using LED signal indications, using larger signal indications, using an additional red-signal indication to each head or adding backplates. Typical traffic-signal backplates are painted black to provide a dark background; however, additional measures can be taken to make the backplate more conspicuous. A study found that adding a yellow, diamond-grade reflective tape to the traffic-signal backplates at several intersections helped reduce insurance claims due to crashes at affected intersections.

Real-world effects

A “before-versus-after” approach was used to determine if red-light running or right-turn-on-red violations were affected by the LSBS or LED backplate. In order to quantify the number of red-light running and right-turn-on-red violations occurring at the intersection, a video camera was set up to record the approach to the study intersections.

For the purposes of this study, a driver made a red-light-running violation if that person’s vehicle was completely behind the painted stop line after the onset of the red traffic-signal indication and if that vehicle continued and completed the desired movement through the intersection during the red traffic-signal indication. These red-light-running violations did include a small number of turning vehicles, but nearly all of these violations occurred soon after the signal indication changed to red.

A driver making a right-turn-on-red violation stopped or slowed, paused and then continued to make a right turn during the red-signal indication. Unlike red-light-running violations, right-turn-on-red violations were not limited to occurring just after the change to the red-signal indication. These violations were noted as occurring throughout the duration of the red-signal indications.

Lighted stop bar system (LSBS)

Video was recorded for the Jefferson at Main intersection from Jan. 25 to Feb. 1, 2006, with three weekdays analyzed to determine the number of vehicles, LRVs, traffic-signal cycles and motor vehicle violations per day (before data). The LSBS was turned on for Jefferson Street on March 25, 2006, and three days of “after” data was subsequently analyzed from video recorded between March 22 and March 28, 2007. During the study period, no major changes to roadway geometry, traffic-signal hardware, traffic-signal phasing or traffic volumes were noted. The only noticeable change was the addition of the LSBS. The types of violations recorded were: vehicle runs red light and vehicle makes right turn on red, which is an illegal maneuver at this approach.

In order to determine if any differences exist in the data, the t-Test statistical test was used. Specifically, the pooled t-Test was used to determine if a significant difference in means existed between the number of violations before and after the activation of the LSBS. The number of red-light-running and right-turn-on-red violations per day was compared between the before and after time periods.

In addition to monitoring violations through video, crash records also were obtained from Metro detailing each crash along the rail line from the time the rail line was opened to the public. These records include crashes of motor vehicles with trains, motor vehicles with other motor vehicles and other crashes. Because of the small number of crashes occurring over time at these intersections, the crash records provide results that are supplemental to the results from the monitoring of violations. Crash statistics were compiled to provide the number of crashes both before and after the LSBS was activated for Jefferson.

The intent of placing these devices on Jefferson was to reduce red-light-running crashes at the approach to Main Street (and the Metro rail line); therefore, the only crashes relevant for this crash analysis are the “Ran Red Light” crashes. These are eastbound Jefferson crashes that resulted from a motorist running through a red light.

There was one eastbound red-light-running crash at Jefferson in the 12 months before activation, and there were no red-light-running crashes in the 12 months after activation. The crash totals for this intersection are low for both the before and after periods, and the number of red-light-running crashes did not increase over time.

LED-outlined traffic-signal backplates

The methodology used to evaluate the LED backplates was similar to that used to evaluate the LSBS. Video was recorded of the Gray Street at Main Street intersection from Jan. 25 to Feb. 2, 2006, and three 24-hour periods were analyzed to determine the vehicle and LRT activity, as well as motor vehicle violations per day (before data). Three days of after data was analyzed from video recorded between March 21 and March 29, 2007.

Similar statistical tests were used to determine the effectiveness of the LED backplate that was used in the LSBS analysis. The number of red-light-running and right-turn-on-red violations per day were compared between the before and after time periods.

In addition to monitoring violations through video, crash records also were obtained from Metro detailing each crash along the rail line from the time the rail line was opened to the public. These records include crashes of motor vehicles with trains, motor vehicles with other motor vehicles and other crashes. During the immediate 12 months before and 12 months after deployment of the LED backplates, there were no crashes at the intersection attributable to red-light-running or right-turn-on-red violations.

Future-world plans

Based on the initial study results, it appears that the lighted stop bar system has significantly reduced right-turn-on-red violations at the study intersection, and while there was a noted reduction in red-light-running violations, this reduction was not statistically significant.

Conversely, it appears that the LED-outlined traffic-signal backplates significantly reduced the number of red-light-running violations. Although there was no statistically significant reduction in the number of right-turn-on-red violations for the LED-backplate treatment, there was a reduction in total average right-turn-on-red violations per day.

Metro is currently expanding the experimental use of both of these treatments, and the evaluation of their effectiveness is ongoing. Both of these devices are slated for strategic use on Metro’s proposed four new light-rail lines in Houston.

“Currently we have TTI [Texas Transportation Institute] evaluating the real-world effectiveness of these technologies, and based on their findings, it has been very effective to date,” said Walter Langford, Houston Metro’s senior project manager of traffic-signal programs. “Once all the data is analyzed, we will use the information to proceed to the next step in the process of incorporating these items into the Texas Manual on Uniform Traffic Control Devices as a standardized safety device.”

Metro has used their experience with the lighted marking systems to work with vendors to improve performance, operation and maintenance capability. The LSBS evaluated as part of this report could be considered Generation 1.0. Metro has evolved to Generation 4.0 over the past three years as changes have been made in installation, operation, controller and active management capability.

One proposed improvement to both the LSBS and LED backplates would be to have them display yellow in a steady state during the yellow interval of the traffic signal in addition to displaying red during the red interval of the traffic signal. Presumably, some red-light-running violations take place because the yellow traffic-signal indications may not provide adequate visibility. Currently, the LSBS and LED backplates presented red to the driver as the signal turns red, but if the stop bars or backplates were to display yellow on the change interval, more drivers may notice the onset of the yellow indication (or at least notice the yellow indication earlier). Although this type of activation and operation has yet to be evaluated extensively, it is suspected that it could help produce reductions in red-light running.

About the author: 
Voigt is a research engineer with the Texas Transportation Institute, Houston. He can be contacted at [email protected]?.edu. Tydlacka is an associate transportation researcher at TTI. He can be reached at [email protected]
Overlay Init