Tests show effectiveness of police cruisers’ flashing blue lights in freeway work zones

Updated Jun 9, 2018

construction zone, police lights flashing
The Florida Department of Transportation has released a report that shows flashing blue warning lights on stationary police vehicles cause drivers to slow down in freeway work zones.

The project found speeds reduced by three to four miles an hour in vehicles that approach highway work zones with flashing blue lights.

Data were collected for two weeks prior to the deployment of a police vehicle, two weeks during which a police vehicle with flashing lights was stationed at the work zone, and two weeks following the removal of the police vehicle, the agency says.

The effectiveness was evaluated based on reductions in average vehicle speeds, reductions in vehicle speeding and changes in vehicle lane use.

This project was funded by the Research Center of FDOT and directed by Darryll Dockstader, Research Center manager. The overarching goal is to use the research to help reduce the number of accidents involving freeway work zone drivers and workers.

Two main safety measures for reducing work zone crashes and their severity have been to reduce the vehicle speeds in work zones and to increase the separation between the vehicles and the workers, the researchers say.

To see their report, click here.

As Florida is one of the states with a Move Over Law, the use of blue lights not only may help reduce vehicle speeds, but may also cause drivers to change lanes away from the active work area when such lanes are available – thus providing additional protection for the workers, the report says.

“This project attempted to assess the effectiveness of deploying stationary police vehicles with flashing blue warning lights in freeway work zones,” says the preliminary NTSB report.

The 16-year-old Florida law states that “drivers must vacate the lane closest to the stationary emergency vehicle, tow truck, sanitation, or utility vehicle. Drivers must slow down to a speed of 20 mph below the posted speed limit if they cannot move over safely.”

Work zone accidents remain a pressing concern in the roadbuilding industry, with groups such as the National Asphalt Pavement Association (NAPA) urging members as well as the public to focus more on safety this year.

In April, NAPA announced a campaign with a video aimed at getting distracted drivers to put down their phones and pay extra attention when they see the cones.

In the new Florida project, each of the two locations under study had flashing blue lights deployed in highway work zone sites.  Below is the report’s summary of key results:

Daytona Beach study location

The key results from the I-4 study location in Daytona Beach (1-lane closure out of three lanes) are summarized below.

1. The deployment of a Florida Highway Patrol (FHP) vehicle with blue lights at the study location reduced the average speed within the work zone by about 4.4 mph.

2. During the two-week period following the removal of the FHP vehicle with blue lights, the average speed within the work zone was reduced by 1.4 mph when compared to the baseline data from the first two weeks.

3. The deployment of the FHP vehicle with blue lights reduced vehicle speeding (i.e., >65 mph) by 20 percent.

4. The deployment of the FHP vehicle with blue lights at the study location shifted only a very small percentage of vehicles away from the work zone. However, this result was not considered reliable due to a large percentage of vehicles that pre-positioned themselves on the inside lane to use the left-side off-ramp to head northbound on I-95.

Gainesville study location

The key results from the I-75 study location in Gainesville are summarized below. These are for 2-lane closure (out of three lanes):
1. The deployment of a Florida Fish and Wildlife Conservation Commission (FWC) vehicle with blue lights at the study location reduced the average vehicle speed within the work zone by about 3.8 mph. This is a slightly lower reduction compared to the 4.4 mph from the Daytona Beach study location.

2. During the period following the removal of the FWC vehicle with blue lights, the average vehicle speed within the work zone was reduced by 2.7 mph when compared to the baseline data from the first two weeks with no blue lights. However, this reduction was derived based on more limited data available for the period following the blue light deployment and is not considered reliable.

3. The deployment of the FWC vehicle with blue lights reduced vehicle speeding (i.e., >60 mph) within the work zone by about 16 percent. Below are results of a 2.5-lane closure (out of three lanes):

  • The deployment of FWC vehicle with blue lights at the study location reduced the average vehicle speed within the work zone by about 2.8 mph.
  • During the period following the removal of FWC vehicle with blue lights, the average vehicle speed within the work zone was reduced by 3.1 mph when compared to the baseline data from the first two weeks with no blue lights.
  • These results for 2.5-lane closure are not considered reliable as the baseline data from the period before the blue light deployment came from just one night closure.)
  • The deployment of FWC vehicle with blue lights reduced vehicle speeding (i.e., >60 mph) within the work zone by about 10 percent.