Making Intersections Safer: A Toolbox of Engineering Countermeasures to Reduce Red-Light Running
An Informational Report
Chapter 4 - Red-Light Running Problem Identification and Resolution Process
The solution to the red-light running problem involves a combination of education, enforcement and engineering measures. The focus of this report has been on engineering countermeasures, which were identified in Chapter 3. This chapter presents information on how an agency can identify the existence of a red-light running problem and then select the most appropriate countermeasure or a combination of countermeasures.
Governmental agencies may first install automatedenforcement systems at red-light running problem locations without investigating whether or not there are any engineering deficiencies and/or if certain engineering countermeasures can reduce the incidence of red-light running. Prior to the installation of red-light running cameras, an engineering study should be performed. This study should determine whether the red-light running problem is a design/operational issue (requiring engineering) or a behavioral issue (requiring enforcement and education). It is first necessary to verify that an intersection has been properly designed and constructed and that there are no engineering deficiencies that contribute to the red-light running violations.
The intent of this chapter is to provide a process to be followed to systematically address a red-light running problem at a signalized intersection. The process of investigating an intersection, looking for engineering deficiencies and implementing engineering countermeasures is known as an intersection engineering study. The goal of an engineering study is to identify the most effective solution to an identified problem. In this case, the problem would be red-light running. The solution could include engineering, education, or enforcement countermeasures.
A distinction should be made between a red-light running "problem" at a specific signalized intersection or a system-wide problem within a jurisdiction or area. It appears that the incidence of red-light running is increasing along with other traffic violations, collectively described as aggressive driving behaviors. If true, this increase should be experienced at a majority of signalized intersections. If that is true, then there needs to be a system-wide solution set that would consist of a combination of engineering, education and enforcement measures. The discussion that follows, however, deals with specific intersections.
The process for addressing a safety problem related to red-light running is the same as would be for any identified safety problem. From an engineering perspective, it includes the following activities:
How these elements can be pursued for a red-light running safety problem is discussed below.
Red-Light Running Problem Identification
At any given signalized intersection there is likely to be some amount of red-light violations. There are also likely to be some number of crashes related to red-light running, notably angle-type crashes. Logically, the two are related with increasing violations begetting increasing crashes; however, the exact relationship has not yet been established.
The issue here is whether or not the frequency of one or both measures, violations and crashes, is high enough such that it signals a red-light running problem-that being a frequency that is higher than what would be expected. If a specific intersection has a red-light running problem, then how should the engineer, in concert with law enforcement, address the problem until it is sufficiently mitigated?
The initial identification of a red-light running problem can come from several sources, singularly or in combination as illustrated in Figure 4-1. Citizens, either as drivers, pedestrians, or bicyclists, can complain about a specific intersection having too many motorists running the red-light. These complaints can be directed to either the local engineering office, the police, or to elected officials. Police can become aware of problem intersection either through citizen complaints, their own patrolling and monitoring, or from high accident location identification programs of their own or the engineering department. The engineering office may become aware of a potential problem in a similar fashion as the police. Quite often, elected officials may be most vocal about a red-light running problem that needs to be corrected.
However, to determine if there is indeed a red-light running problem, a traffic engineering analysis should be performed. A specific signalized intersection could be considered a red-light running problem if it is experiencing a level of violations or related crashes that is greater than some selected threshold value. Threshold value criteria, such as higher than the average or some other statistic, for violations and/or related crashes should be established and applied to quantify that there is a red-light running problem. For violations, a value could be based on local police experience. Law enforcement agencies would have data on citations issued for various traffic violations and may be able to establish if a given intersection has a higher than average violation rate. Based on the literature, violation rates can vary significantly and are likely dependent upon a number of factors. Some violation rates, in terms of violations per approach volume or per time period were presented in Chapter 2.
For crashes, the investigating agency should isolate redlight running related crashes. The ability to identify a crash that was a result of running a red-light is dependent upon the type and accuracy of the information recorded on the police report. Indicators of a red-light running related crash can be found in several sections of the report, depending upon the state, and include: contributing cause (e.g. failed to yield right of way, disregarded traffic signal), collision type (e.g. angle, left, or right turn), traffic control (i.e. presence of traffic signal), offense charged and the narrative and diagram. However, all of these data elements may not be coded or available to the analyst who is using only the coded file to identify red-light running crashes. If the analyst does not have access to the police report, angle-type crashes that are coded as occurring at an intersection, with a traffic signal and a driver action that would indicate disregard of the signal, would likely be a red-light running related crash.
To be a problem, red-light running related crashes could be either high in frequency, high in rate based on intersection entering volume, or high in comparison to other types of crashes related to the intersection. Bonneson (39) indicates that typical intersection approaches experience 3 to 5 red-light runners per 1,000 vehicles. Using a rate statistic for this assessment is preferred, but it requires having timely traffic volume data that may not be readily available. An alternative method would be to compare the percentage of red-light running related crashes to other crash types at the intersection. This comparison would be made against an intersection crash type distribution developed by the respective agency, where the data distribution is more representative of local intersection characteristics. If the percentage of angle crashes was much higher than the value for the distribution found for all similar intersections in the jurisdiction, than this could indicate a red-light running problem.
The data should be evaluated to determine if a red-light running problem exists. If not, then attention can be turned to other problems that might exist at the intersection and countermeasures to address those.
Site Evaluation to Identify Deficiencies and Engineering Countermeasures
If there is a confirmed problem, then the engineer should identify the factors that are contributing to the problem and then evaluate possible countermeasures in a systematic method. The initial step for this evaluation is to conduct a field review and collect the necessary data that would isolate any deficiencies. As a minimum, the data and assessments that will be needed include:
The engineer can refer to the ITE publication, Manual of Transportation Engineering Studies (39) regarding methods and procedures for collecting various traffic related data.
In addition, the engineer should spend some time observing the traffic flow and the occurrence of redlight running at the intersection. An hour or two of onsite observation could confirm the existence of red-light running; indicate the principal kind of red-light running event (whether or not the event appears to be intentional); and possibly how these contribute to crashes. A formal traffic conflicts study as described in the ITE Manual of Transportation Engineering Studies could be conducted as well. These observations will provide a sense for the traffic operational characteristics of the intersection and may offer potential clues to problem identification and solution.
One of the first considerations is to confirm that the traffic signal is still warranted. It would be unusual for a signalized intersection to have a red-light running problem where the signal is not warranted because of low traffic volumes. Still, this preliminary assessment, which can be made easily, is suggested. If there is a possibility that the signal is not warranted, then further studies are recommended. (See reference 57 for guidance on removing unwarranted traffic signals). However, even if it is decided to investigate the possibility of signal removal, the engineer should proceed with the following field review.
A field review of the problem intersection is necessary to better understand the characteristics of the problem, to isolate deficiencies and to identify potential countermeasures. Sufficient time should be allocated to conduct a thorough review of the intersection. This means that the review may have to occur during different times of the day to observe operations and conditions under different levels of traffic flow and ambient light.
Figure 4-2 provides a listing of items that should be checked while at the intersection. They are discussed below with consideration to the alternative countermeasures discussed in Chapter 3 to resolve identified deficiencies.
Check for Signal Visibility
There are several visibility features that should be checked. The sight distance to the traffic signals should be determined and compared to the minimum sight distance requirements shown in Table 3-1. Keep in mind that this will require a knowledge or good estimate of the 85th percentile speed of approaching traffic. If the minimum sight distance is not available, there are a number of countermeasures discussed in Chapter 3 to consider:
While the visibility distance may be adequate, there may be obstructions to full and continuous visibility. Oftentimes, as shown in Figure 4-3, utility wires can limit the visibility to the signals. Resolution of this problem may require repositioning of the signals vertically or horizontally or, as was the case shown in Figure 3-9, installing a supplemental signal.
The next visibility feature would be the positioning of the signals to ensure they meet the cone of vision requirements and the minimum and maximum distances from the stop bar. Resolution of any deficiencies noted here would include:
Next, would be to check that there is an adequate number of signal heads. While a minimum of two are required for the major movement, consideration should be given to providing one for each lane where there are three or more lanes and that they are centered over the lane.
When programmable signals are used to avoid confusion, their visibility sight line should be checked. The provided sight line should be as long as possible without conflicting with other signal displays.
The brightness level of the signals should be viewed during varying ambient light conditions. Standard incandescent bulbs will deteriorate over time and need to be checked on a periodic schedule. The solution will be to replace the bulbs in a timely fashion or consider use of LED signals. While these types of signals will eventually fail, they hold their brightness level for a much longer period.
Check for Signal Conspicuity
While the signal display may meet all the visibility requirements noted above, the signals still may not be conspicuous-the ability to stand out amongst competing light sources or other information sources that compete for the motorists' visual and driving attention. Often times when the environment around the intersection is visually cluttered, the motorist can be distracted and not see the traffic signal until well into the dilemma zone. Visual competition can come in many forms. In suburban, high-density commercial corridors, there may be many other light sources from advertising signs and the like. Large overhead traffic guide signs may draw the attention of unfamiliar motorists placing more attention to navigation than intersection control. Whatever the situation, there are a number of countermeasures designed to draw the attention to the traffic signal. In addition to those noted for improving signal visibility, these would include:
In addition to making the signals as visible and conspicuous as possible, the engineer may determine that it is necessary to get the motorists' attention as they approach the intersection. This can be accomplished a number of ways to include amber flashers on a SIGNAL AHEAD sign and advance warning flashers.
On rare occasions, some engineers have installed strobes in their red-lights for the purpose of its attention-getting values. However, as noted in Chapter 3, these are not sanctioned by the MUTCD and, therefore, their use should be restricted to special circumstances. Also, rumble strips have been used in rare instances to gain the attention of approaching traffic and to reduce speed. As noted in Chapter 3, there are no known evaluations of their effectiveness and, hence, their use should be restricted to special situations. They are not suggested for high-speed (greater than 45 mph) facilities.
Check Signal Control Parameters
Having identified any visibility or conspicuity issues, the engineer should review the various traffic signal control parameters. The occurrence of red-light violations is affected, in part, by signal control parameters, specifically the change period interval and the cycle length and phasing. These are discussed below.
Change Interval Review
Probably the most significant factor that affects the incidence of red-light running is the duration of the yellow change interval. Hence, this aspect of signal operations should be reviewed for adequacy. The yellow change and all-red clearance interval was discussed in Chapter 3. Using either the agency's established procedures or procedures provided in publications such as the ITE Traffic Engineering Handbook (44), the engineer should determine if the yellow change interval is appropriate for the conditions. If the yellow change interval is within the guidelines, then the engineer may want to consider further increasing the interval, but likely no more than 1 additional sec. If it is below the guidelines, then the yellow change interval should be increased to that level. Care must be exercised when using a long yellow change interval, say 5 sec. or greater. Frequent drivers may realize the signal has a long yellow display and take advantage of it by continuing through the intersection, instead of coming to a stop. As a result, it may be appropriate to shorten the yellow change interval (yet, with respect to guidelines) and add or increase an all-red clearance interval to discourage inappropriate driver behavior.
Additionally, the all-red clearance interval should be reviewed, assuming one is being used. As discussed in Chapter 3, an all-red clearance interval is that portion of a traffic signal cycle where all approaches have a redsignal display. The purpose of the all-red clearance interval is to allow time for vehicles that entered the intersection during the yellow change interval to clear the intersection before the traffic-signal display for the conflicting approaches turns to green. While the use of an all-red does not eliminate red-light running, its use can prevent a crash for the violator entering the intersection just as the signal turns red. Please refer to the ITE publication, Traffic Engineering Handbook (44), concerning procedures on the application of the all-red clearance interval.
Cycle Length/Phasing Review
The traffic-signal cycle length and phasing should be reviewed. If the intersection operates within a coordinated signal system, then these two components would not likely be changed so as to disrupt progression and overall system efficiency. If the intersection is operated in isolation, then the engineer may want to consider reducing the cycle length if it is long (180 sec. or longer), or increasing the length if short (60 to 90 sec.). The possible effect of long and short cycle lengths is discussed in Chapter 3. Unexpected signal phasing sequences may contribute to red-light running and this should be examined as well.
Check Geometric Features
There are at least two geometric features that should be reviewed as they may have an effect on red-light running, namely:
Check Traffic Operational Features
As a minimum, the following traffic operational features should be examined:
Other Countermeasures To Consider
If after all the viable relatively low-cost engineering countermeasures described in the first part of this chapter and in Chapter 3 have been tried without success in eliminating the problem, then there are a variety of additional measures to consider. These include more extensive re-engineering measures, or enforcement countermeasures.
Re-Engineering of Intersection
Consideration should be given to a redesign of the intersection, if appropriate. This may involve physically improving the sight distance, if that was the problem, by a change in approach curvature and/or grade profile. This is obviously an expensive countermeasure and would require an in-depth engineering analysis to support such a decision. Also, the agency may want to consider replacing the signalized intersection with an alternative intersection design or possibly a roundabout, but again, a more comprehensive study would be needed, and quite likely there would have to be other problems beyond the redlight running issue to justify such an expensive treatment.
Increased enforcement should be considered if the engineering measures do not resolve the problem or until the engineering measures can be installed. Traditionally this would include selective enforcement by the police. Some cities have begun to develop specific task forces to address traffic issues and violations. Some of these special tasks often include target enforcement of red-light violations at particularly dangerous locations with a high number of violations. However, this type of measure is usually transitory in effectiveness, and can itself be hazardous because police have to follow the offender through the intersection exposing them to potential collisions.
To counter this problem, some jurisdictions use a redlight detector and enforcement light, known as a "rat box" or "red eye" unit. Figure 4-4 shows the placement of a rat box at an intersection. Figure 4-5 shows the enforcement light being used in the City of Richardson, TX. With this device, a light is attached to a pole that is activated when the red is on. This allows the police to position themselves on the far side of the intersection, which precludes the need to follow the offender through the intersection.
If the jurisdiction already has an automatedenforcement program using cameras, then they should consider adding the problem location into their program. In so doing, the jurisdiction might want to use the following examples as a guide.
Maryland State Highway Administration Criteria for Installation of Automated Systems
The Maryland State Highway Administration (MDSHA) does not install automated systems, but does allow local jurisdictions to use them at intersections with a state road under certain requirements. MDSHA has developed a number of principles for the use of redlight camera systems, which are enumerated below:
State of North Carolina Policy on the Use of Automated Systems
In developing a recommended policy for the use of automated systems for the state of North Carolina, Milazzo et al. (10) recommended an eight-stage process to be followed for systematically solving a red-light running problem. It is enumerated below:
Milazzo et al. also suggest the following types of locations may be appropriate for camera installation pending the results of an engineering study:
What has been presented in this chapter is a process for determining if a red-light running problem exists and what types of countermeasures could be implemented in a logical and systematic manner. Individual agencies may have already established procedures for conducting audits and review of problem intersections that may accomplish the same objective. The goal of this process is to identify the most effective solution to an identified red-light running problem. The solution could include engineering, education, or enforcement countermeasures.
How to drive a roundabout (WSDOT)