U.S. flag

An official website of the United States government, Department of Justice.

Police Roadside Safety: Tools to Increase Visibility

Date Published
June 27, 2010

To be seen or not to be seen: for law enforcement officers, that is the question. Officers' lives depend on their ability to be covert sometimes and visible other times, depending on their task. Keeping themselves and their vehicles visible when stopped on the side of the road is an essential safety consideration for law enforcement officers.

A vehicle's size and color, the weather and the time of day affect whether drivers can easily see emergency vehicles and responders. Emergency vehicles have features that draw attention to them even when drivers are not specifically looking for them. Typical features include warning lights, sirens and horns, and retro-reflective striping (striping that reflects light back to its source).

Firefighters, in contrast to law enforcement, always need to be visible on the job. They follow a national “Standard for Automotive Fire Apparatus” issued by the National Fire Protection Association. Though observance of the standard is voluntary, most manufacturers of firefighter vehicles comply in order to limit liability and ensure their products will sell.[1]

Unlike firefighters, law enforcement officers do not have national visibility standards. Many law enforcement agencies voluntarily apply retro-reflective markings to patrol cars, motorcycles and other vehicles. [2] Some agencies position these markings so that vehicles might remain unseen at times, depending on the vehicle's angle. NIJ funds research, including an evaluation of current initiatives by local and state agencies, to help refine and develop visibility tools for law enforcement.

NIJ funds studies on the effectiveness of tools to increase the visibility of law enforcement officers and their vehicles. These tools include:


NIJ's Emergency Vehicle Visibility and Conspicuity Study examines whether retro-reflective striping (striping that reflects light back to its source), high-visibility paint, built-in lighting and other reflectors make emergency vehicles more visible and improve roadway safety. The U.S. Fire Administration and the International Fire Service Training Association conducted the study, which was published in August 2009.

Researchers found that:

  • Retro-reflective materials can help increase vehicle visibility, especially at night.
  • Contrasting colors on public safety vehicles help civilian drivers spot hazards on the roadway.
  • Fluorescent colors (especially fluorescent yellow-green and orange) offer higher visibility during the day.

Read the full report, "Emergency Vehicle Visibility and Conspicuity Study" (pdf, 45 pages).

Warning Lights

NIJ funded a study to examine how the color and intensity of warning lights affect driver vision and emergency vehicle safety during both day and night.

Researchers found that study participants:

  • Could find warning lights at night regardless of the lights' intensity.
  • During the day, however, higher intensity lights improved drivers' ability to spot the lights.
  • Blue was the easiest color for participants to see, day and night.
  • Warning lights had little effect on the ability to see responders during both day and night.

The U.S. Fire Administration, the International Fire Service Training Association and the Society of Automotive Engineers conducted the October 2008 study.

Highway Flares

Law enforcement officers use flares to increase visibility and point out accident locations and other traffic hazards.

Magnesium-based highway flares, the type most commonly used, can create risks for both officers and the surrounding area. The flares burn at high temperatures for 15 to 30 minutes, creating smoke and fumes that can overwhelm the officer. Magnesium-based flares also have potential long-term effects on surrounding soil and water; for example, the byproducts of burning flares can poison a water supply.

NIJ funded a study on highway flares that use chemical or electric sources of energy, and thus do not carry the same risks. The study found that the chemical and electric flares were less visible than traditional flares when placed at ground level. However, when the same flares were placed on a cone, they were visible from a distance of at least 1 mile.


Drivers might not see first responders working on the side of the road, especially in low-light conditions and when they are distracted by flashing vehicle lights. High visibility garments such as vests with retro-reflective striping significantly increase the chances of first responders being seen by other drivers. A special public safety vest for law enforcement officers has been developed. According to a video on ResponderSafety.com, the vest is easy to don and remove, allows easy access to weapons and offers 360-degree visibility.

A Department of Transportation regulation, effective as of Nov. 24, 2008, requires that "anyone working within the right-of-way of a Federal-aid highway will be required to wear high-visibility clothing." The regulation applies to all emergency responders, including law enforcement officers who are directing traffic, investigating crashes, and handling lane closures, obstructed roadways and disasters within the right-of-way of a federal-aid highway.

The regulation, however, does not apply to law enforcement officers who are performing duties — e.g., traffic stops, searches, manhunts — that place them in an adversarial or confrontational role. Exceptions to requirements to wear visible clothing were granted in response to concerns raised by state, local and national police organizations, as well as state departments of transportation, that reflective garments would make law enforcement officers better targets if a gunfight were to develop, especially at night.

Date Published: June 27, 2010