Red-Signal Enforcement Lights

Purpose

Red-Signal Enforcement Lights enhance safety at signalized intersections by improving 

red-light compliance, resulting in a reduction of red-light running violations. They are 

auxiliary lights connected to a traffic-control signal to help law enforcement officers more 

efficiently and safely issue citations for drivers who violate the red phase of the signal. 

According to the US Department of Transportation’s Fatality Analysis Reporting System 

(FARS), 869 people were killed in crashes that involved red-light running in 2006, and 

the National Campaign to Stop Red-Light Running estimates that another 143,000 were 

injured. 

Alternative Names

Red light indicator lights, red light indicators, signal indicator lights, enforcement lights, 

white enforcement lights, rat lights or boxes, tattletale lights.

Operation

The Red-Signal Enforcement Light activates simultaneously with the red signal phase, 

providing an enforcement officer located downstream from an intersection with a visible 

indication of the upstream red phase so they can determine when a vehicle has violated 

the red phase. Relatively small, low-cost lights are mounted on the top, bottom, or rear 

of a traffic signal and are wired into the signal controller for accurate red-signal phase 

indication. Red-Signal Enforcement Lights should not be colored red, yellow, or green, in 

order to avoid confusion with traffic signal control indications.

Potential Benefits

Red-Signal Enforcement Lights can provide safety, efficiency and/or cost benefits, 

compared to other enforcement methods. These benefits include:

• Allowing red-light running monitoring from any leg of an intersection, particularly downstream 

from the intersection;

• Eliminating the need for unsafe pursuit by single upstream officer across the intersection during 

the red phase;

• Allowing one patrol officer instead of two (downstream) to enforce a traffic-control signal, thus 

increasing enforcement resource efficiency and versatility;

• Having lower installation and maintenance costs than automated enforcement systems, 

potentially allowing more numerous installations; and

• Do not use potentially controversial automated photography.

This summary is one in a series 

describing Innovative Intersection 

Safety Treatments. The summaries 

identify newer technologies and 

techniques to improve intersection 

safety developed since NCHRP 

Report 500, Volumes 5 and 12, 

were published in 2003 and 2004, 

respectively. These treatments 

show promise for improving safety 

but comprehensive effectiveness 

evaluations are not yet available.

May 2009

FHWA-SA-09-005
Agency Experience

• A Florida Department of Transportation study showed installation of Red-Signal Enforcement 

Lights, coupled with aggressive enforcement, reduced the annual number of red-light 

violations by 25 percent (“A Study of the Effectiveness of White Enforcement Lights,” Florida 

Department of Transportation, 2008). The lights are installed at more than 500 intersections 

across Florida. 

• The city of Clearwater, FL also found a significant drop (as much as 50 percent) in red-light 

running at intersections where Red-Signal Enforcement Lights were used.

• Richardson, TX has installed Red-Signal Enforcement Lights at more than 40 intersections, and 

there have been more than 100 installed across Santa Clara County, CA.

Implementation Considerations

• There are no compliance issues with the Manual on Uniform Traffic Control Devices, as RedSignal Enforcement Lights are not traffic-control devices.

• Red-Signal Enforcement Lights are only effective when combined with red-light running 

enforcement efforts by enforcement officers.

• Red-Signal Enforcement Lights should be positioned to be visible to downstream enforcement 

officers while minimizing distraction or confusion to drivers. Officers must simultaneously be 

able to see the intersection’s upstream stop bar from downstream—this can, if necessary, be 

facilitated by the use of traffic cones or flexible traffic posts.

• Red-Signal Enforcement Lights must be high enough to be seen over tall vehicles and out of 

reach of vandals. 

• Wiring should be connected to the controller output for the red-signal phase to power the 

Red-Signal Enforcement Light simultaneously.

• Red-Signal Enforcement Lights are visible from a full 360 degrees but may be partially “taped,” 

or installed with alternative housing configurations, to control visibility and reduce potential 

driver distraction. 

• Warning and regulatory signs supplementing Red-Signal Enforcement Lights can remind 

drivers of red-light running enforcement or fines.

• Attainment of judicial support for prior acceptance of the citations given based on the 

enforcement lights is critical for optimal effectiveness of the lights. Public awareness 

campaigns may also increase effectiveness.

Costs

• Red-Signal Enforcement Light sets (including housing) cost approximately $50–$150 for 

traditional (rather than LED) bulbs. 

• Generally, 4 to 8 indicator sets are needed for a major intersection to cover all signal phases for 

a total intersection cost of $200-$1,200. 

• Cost depends substantially on whether LED or traditional bulbs are used. LED bulbs cost 

approximately three times as much initially, but require much less power.

Figure 1: Bottom-mounted Red-Signal 

Enforcement Light on a signal head

Figure 2: Red-Signal Enforcement Light mounted 

top-rear at a signal head

Learn More

Peter Hsu, Florida Department of Transportation

ping.hsu@dot.state.fl.us 

http://www.dot.state.fl.us/Safety/CTST/

downloaddocs.shtm

Jeffery Smith, San Jose Traffic Enforcement Unit

jeffery.smith@sanjoseca.gov 

http://www.sjpd.org/BFO/SpecialOps/TEU/

Red_Light_Enforcement.html 

Ed Rice, Intersection Safety Team Leader 

FHWA Office of Safety

202-366-9064 

ed.rice@dot.gov