Traffic speed in highway work zones

by Jim Zaichkowski, CSAO

 

We all know it. A lot of drivers speed through highway construction zones. The hazard to workers is clear—you need only look at the number of crushed barrels or scuff marks on concrete barriers as you’re driving by.

The industry needs to find solutions that will protect workers. But the first step is getting the facts.

In 2002 and 2003, CSAO collected data at a number of highway construction zones around Ontario.

The sites we studied had the following characteristics:

• lane width reduction or lane closures
• a reduction in the posted speed limit
• a traffic control plan that’s approved by the Ontario Ministry of Transportation and properly set up
• construction along all or portions of the work zone.

CSAO installed one electronic data collector in the centre of each active lane of traffic. These devices record vehicle speed, vehicle size, the temperature, and whether the pavement is wet or dry.

From the table below, you can see that the percentage of vehicles traveling over the reduced posted speed limit varies considerably.

* For a reduced speed limit (RSL) of 80 km/h, driving over 88 km/h was considered speeding. For an RSL of 70 km/h, driving over 79 km/h was considered speeding. For an RSL of 60 km/h, driving over 71 km/h was considered speeding.

First, let’s look at secondary highways. Four of the five secondary highway lanes we studied had the lowest percentage of vehicles travelling faster than the reduced posted speed limit, ranging from about 4% to 14%. The one exception was a secondary highway where about 66% of all vehicles sped through the zone.

In the two primary non-freeway highways we studied, the percentage of vehicles that were speeding varied widely—ranging from a low of about 24% to a high of 85%.

The three 400-series highway sites also had a large variance: from 27% to 79% of vehicles sped through the zones.

If you count all of the vehicles that sped through all of the work zones we studied, and divide that figure by the total number of vehicles that drove through the zones, the overall percentage of vehicles traveling faster than the reduced posted speed limit was about 48%.

Highway construction zones are often difficult to navigate. They can present the driver with narrow lane widths or lane closures, message boards, arrow signs, lane delineating barrels, and traffic cones. Reducing the speed limit in work zones is an attempt to give drivers time to react to these abnormal conditions. So when 48% of vehicles are speeding through these conditions, both drivers and workers are at risk.

CSAO’s study indicates the extent of the problem. Our next step is to find practical and effective methods to control vehicle speeds in work zones. We need your help with further research in 2004. For more info, contact Jim Zaichkowski at 416-679-4052, jimza@csao.org.