Monash University Accident Research Centre – Report #73
Authors: S. Kent, B. Corben, B. Fildes & D. Dyte
Abstract:
One of the key enforcement initiatives intended to reduce the number and severity of intersection crashes is Red Light Cameras. There are currently about 120 Red Light Camera intersections covering metropolitan Melbourne and Geelong.
The objective of this study was to determine the nature and extent of red light running behaviour at a sample of camera and comparable non-camera sites around Melbourne. Signal compliance was measured as a function of speed zone, road cross section, lane type, time of day and day of week.
Three intersections were investigated. For each intersection, measurements of red light running behaviour were obtained by video-taping traffic at three selected approaches, namely the camera approach, the opposite (non-camera) approach at the same intersection (i.e., subject to the red light camera ahead sign but with no camera) and also a matched approach with no signs or camera. Red light running was a relatively rare occurrence (123 encroachments out of 38,000 observed vehicle movements – 0.32%); Further, 93% of the encroachments occurred during the all-red period of the signal cycle when the probability of conflicting traffic is lowest.
Red light running rates were significantly higher for right-turn movements compared to through movements. Red light running rates were also higher for right-tum movements in 60 km/h speed zones, on undivided roads than in 80 km/h speed zones on divided roads. The difference between right-tum and through movement red light running rates was most pronounced in the evening peak period.
Notably, there were no differences in the observed rates of red light running between camera and non-camera approaches. Results are discussed in terms of their implications for further research and for the operation of the Red Light Camera Program in Victoria.
Executive Summary
Red light cameras have been in operation in Victoria since 1983 and currently cover about 120 signalised intersections in metropolitan Melbourne and Geelong. Cameras were originally introduced to reduce the incidence and severity of intersection crashes, particularly cross-traffic crashes.
While there have been some evaluations of the effectiveness of the Red Light Camera Program in reducing intersection crashes, there has never been a detailed study in Victoria of die nature and extent of red light running behaviour.
Thus, the prime objectives of this study were:
- To examine red light running behaviour at a sample of Red Light Camera (RLC) sites in Metropolitan Melbourne and behavioural differences between RLC and Non-RLC sites (including non-camera approaches of RLC sites);
- To investigate the effects of road cross section, speed zone, traffic volume, lane type and day of week on red light running behaviour;
- To examine the relationship between red light running behaviour and crash occurrence at RLC sites in the light of the findings of a recent investigation of the effects of red light cameras on crash occurrence and types (Andreassen, 1995);
- To make recommendations on future directions for the Red Light Camera Program in the light of the findings of the current study.
The study set out to examine red light running behaviour using the SCRAM computer-based network which controls traffic at most of Melbourne’s signalised intersections. It was hoped that red light running behaviour could be efficiently measured via the SCRAM technology which relied on “trailing edge triggering” as vehicles cleared the magnetic loops prior to the intersection stop line. Extensive pilot testing using the SCRAM technology indicated that, in its current form, it was inadequate for the task for the following reasons:
- There was under-counting of total hourly traffic volumes caused by vehicles queuing on the red phase with reduced headways (the detector loops were insensitive to short gaps between vehicles);
- Over-counting of red light runners occurred in instances where vehicles stopped well over the stop line but did not proceed through the intersection;
- Technical difficulties were experienced resulting in the loss of encroachment data.
After discussions with VicRoads and the Victoria Police, a more reliable method was developed based on video recording traffic from an unmarked private vehicle. This procedure proved to be successful although it required considerably more staff time, thereby limiting the design of the study from that originally proposed.
Observations of red light running behaviour were taken at three carefully selected red light camera approaches and six matched non-camera control approaches around Melbourne. Red light running behaviour was measured as a function of speed zone, road cross section (divided or undivided), time of day, day of week and vehicle type.
The results of the study, in relation to the four main objectives were as follows:
Objective 1 – Extent of Red Light Running
Red light encroachments were relatively rare events and, for the most part, those observed were not all that dangerous. However, there was a relatively small number (8 in over 38,000 vehicle movements) that were dangerous manoeuvres during the full-red interval. If this rate is extrapolated to all traffic signal approaches in Victoria, it represents more than 500,000 dangerous encroachments per year. Though not able to be rigorously investigated in this study, there was also a suggestion in the data that trucks may be over-represented in red light running during the all-red interval. The results suggested that a simple, inexpensive countermeasure to reduce crashes resulting from red light running may be to increase the allred periods at signalised intersections by one or two seconds, although the behavioural consequences of this need careful consideration.
Objective 2 – Road and Environment Effects
The speed limit and cross-section of an approach appeared to influence red light encroachments only for right-turners. Arterial roads with 60 km/h limits and undivided roads had higher rates of illegal right-tum encroachments than did 80 km/h and divided roads.
Red light running rates were generally higher in right-turn than in through lanes, but were particularly so during the evening peak period. Further, there were fewer right-turn encroachments at the site where all approaches had fully-controlled right-tum phases.
Interestingly, there were no statistically reliable differences in red light encroachments observed between camera and non-camera approaches. It is unlikely that this could be attributed to traffic flow differences or other environmental influences as these were relatively constant across test and control approaches for any given site. The results suggest some investigation of the current mode of operation of the red light camera program may be warranted.
Differences between week days and weekend days could not be analysed thoroughly because football traffic had an extreme influence on the weekend data, preventing a proper analysis of the red light running behaviour of drivers on weekends. This finding may be highlighting a substantial safety problem associated with football traffic (or sporting event traffic generally) and warrants further investigation.
Objective 3 – Red Light Running & Crashes
Andreassen (1995) found that the installation of RLC’s at 41 sites studied did not result in any reduction in accidents at those sites. Further, he found no significant differences between crashes at RLC sites compared with signalised intersections in Melbourne generally. Thus, there was no need to do an extensive analysis of the correlation between red light running behaviour observed in this study and crashes. Nevertheless, a simple correlation analysis was undertaken for red light running data in the current study and revealed no significant relationship between the frequency of crashes at RLC and non-RLC sites and differences in red light running behaviour.
Objective 4 – Extension of the RLC Program
While the need for more RLC installations was not justified by this, or the recent accident study of Andreassen (1995), nevertheless there are grounds for improving the operation of existing RLC locations. Highest priority should be given to increasing the perceived risk of detection at these sites. This could be done by overcoming existing technical difficulties at some sites, by increasing the level of activity and by supportive publicity. Subsequent testing might then indicate whether there is a need for more RLC installations.
Recommendations
The three basic recommendations from the findings of this study were that:
- An action program be undertaken to improve the effectiveness of existing Red Light Camera operations in Melbourne as outlined above;
- Further research be undertaken to test red light running behaviour more extensively than was possible in this study. A focus on red light running behaviour associated with weekend sporting events and/or heavy vehicles may be especially worthwhile;
- Consideration be given to increasing the duration of all-red periods by one or two seconds, as a simple, inexpensive countermeasure for crashes caused by red light running, taking into account the traffic capacity and behavioural consequences of such a change.
Sponsor: VicRoads, Road Safety Department
Copyright © Monash University Accident Research Centre 1997, all rights reserved.
This report can be found here.