The Tennesean, Nashville, Tenn., reported Monday that authorities may soon impose split speed limits: 10 mph lower for trucks than for everyone else.

Split limits have already been announced for Memphis and Chattanooga. The new limits will become effective this summer. Now, split limits may also apply in Davidson County.
Split limits in Tennessee are ostensibly intended to cut diesel emissions. Officials estimate that cutting truck speeds by 10 mph, the amount of dangerous pollutants dumped into the air would be reduced by approximately 18% or more per truck in Shelby County alone.
Split limit proponents say the new speed limits would play a key role in safety. The state truckers association questions whether it's fair to make its drivers travel slower on the highways than everyone else and says the rule could make the roads less safe.
There are about 90 miles of interstate in Davidson County. About 39% of it is posted at 70 mph and 24% at 65 mph for all traffic, according to TDOT. The rest is 55.
Dave Huneryager, Tennessee Trucking Association president, said the trucking industry is equally concerned about air quality. For instance, by 2007, engines that are mandated to be used in trucks are expected to burn 93% cleaner than the ones being used now.
"I certainly understand why they are doing it," Huneryager told the Tennesean. "Because if they don't improve air quality, they won't have the highway money to spend."
However, truckers oppose cars around them being able to travel 10 mph faster, Huneryager said. "When you have trucks going slower than cars, it can lead to an increased interaction between the slower vehicle and the faster vehicle," he said.
In a separate article in Monday’s paper, The Tennesean quoted Nashville police sources who said officers were prepared to actively enforce lowered truck speed limits should they be imposed.