Lower speeds approved for Tennessee's Shelby County

| 3/15/2005

Heads up, drivers – by early summer the Tennessee Department of Transportation will reduce the speed limit for all vehicles traveling on urban interstates in Shelby County as part of an effort to clean the air. Currently, all vehicles are allowed to drive 70 mph.

Gerald Nicely, Tennessee’s transportation director, announced the authorization for posting 55-mph speed limit signs for large trucks in the county at a press conference March 14 in Memphis, which is part of Shelby County. All other vehicles would have new limits of 65 mph.

About 107 miles of interstate will be affected by the speed limit changes in the county. A section of state Route 385 that runs about 17 miles will also have lower speeds posted.

“After studying the issue we believe that lowering the speed limit for large trucks will make a difference in air quality for Shelby County,” Nicely said. “A study conducted by the Federal Highway Administration shows that reducing truck speed limits by 10 mph can reduce the nitrogen oxide emission factor by approximately 18 percent or more per truck. If we get reductions anywhere close to that level in Hamilton County, it will be worth it.”

Nicely said the reason for also reducing the car speed is “to lessen the difference between the rates at which the two types of vehicles will be traveling.”

Shelby County Mayor AC Wharton requested the lower limit in a letter sent to Nicely last summer. The Tennessee Air Pollution Control Board and Metropolitan Planning Organization backed the change.

Shelby is the second county state officials have sanctioned lower limits for air-quality purposes. Nicely made a similar announcement last month affecting about 57 miles of interstate in Hamilton County, which includes the city of Chattanooga.

Davidson County, which includes Nashville, and Knox County, which includes Knoxville, also have requested speed-limit reductions.

Officials in the state’s largest cities hope the slower traffic will help their areas meet new federal air-quality standards for ozone pollution.

All of Tennessee’s largest metropolitan areas failed last year to meet the new air standards. Failure to develop plans to clean up the air by 2007 could result in an end to industrial expansion and large cuts in federal highway funding for the area.

The speed limit change does not require state legislative approval.