In the movies, a police chase always ends with the bad guy in cuffs seated in the backseat of a slightly scuffed patrol car. In real life, high speed chases are far messier, with one of the greatest risks being a tire blow out - and the ultimate sacrifice potentially an officer's or citizen's life.
Two years ago, as Florida Highway trooper Daryl Haywood raced after a fleeing car along Interstate 4, his patrol car blew a tire, spun out of control and struck a tree. He died instantly and the runaway motorist received 30 years in prison for what would have resulted in a speeding ticket if he'd pulled over when Haywood first flashed his lights.
Unfortunately, stories such as Haywood's are all too common. The poor condition of many roads and the very nature of police work fuel the prospect of a tire blow out.
Police vehicles subject tires to more severe operating conditions than the average passenger car. Over the course of a normal day, police drivers challenge their squad cars on several emergency calls, and perhaps a pursuit or two. These vehicles operate at slow then high speeds, corner quickly, turn on a dime and log considerable miles. Such stresses diminish tire life and performance.
"Two things cause a tire to fail - friction and heat," says Rick Longobart, fleet superintendent for the City of Inglewood, California. "The police vehicle is susceptible to both."
Longobart positions high speeds as the obvious contributor to tire failure - pursuit driving creates friction and friction generates heat. However, he emphasizes tire damage also develops when tires spin wildly as the vehicle rapidly accelerates. "Police tires are either running at high speeds or spinning, and both can cause the tire to fail," he explains.
A tire for every season
All tires are not created equal. The tire that meets the needs of patrol vehicles operating in the scorching desert heat may not be appropriate in a Northwestern drizzle or a Midwestern snow storm. Likewise, tires best suited to the Ford Police Interceptor may not be as highly rated for the Chevrolet Impala, and so on.
Most departments select tires offering both wet and dry performance capabilities, says Lance Miller, testing manager at the National Law Enforcement Corrections & Technology Center (NLECTC), which is a program of the National Institute of Justice that tests technology designed for law enforcement.
"We lack the luxury of driving exclusively in one or the other condition," he explains. "Everyone has to drive in most types of weather at some point, but how much of that you drive in plays a factor in the tire you select."
San Diego averages approximately 9 inches of rain a year. On a rainy day in this sunny, temperate climate, the number of citizen accidents rises 50 to 70 percent as rain water pushes oils and lubricants deep in the asphalt to the surface. Law enforcement vehicles cannot afford to be out of commission during these hectic times because of poor tire selection. By choosing a speed-rated tire, John Alley, San Diego Police Department's police fleet administrator, says squad cars stay on the road.
While maintaining the Washington State Patrol vehicle fleet for three years, Alley notes he employed pursuit-rated dry season tires during the summer months and pursuit-rated snow tires over the winter months. In some areas, Alley fitted studs to the tires to maneuver safely on black ice. "I had to take extra precautions to make sure I had speed-rated snow and mud tires, and studded tires," he says.
Navigating tire ratings
All tires mounted on patrol cars must be rated for pursuit, explains Miller, who headed the bi-annual NLECTC tire testing program from 1995 until the final test in 2001.