Truck Speed Limiters Won’t Improve Highway Safety

The National Highway Traffic Safety Administration wants all heavy trucks to have speed limiters – devices that block big rigs from driving above a certain predetermined speed. The Insurance Institute for Highway Safety – which is also pushing for lower speed limits – and other groups support NHTSA’s planned regulation.

While no one wants to see 80,000-pound tractor-trailers traveling at unsafe speeds, there’s plenty of evidence that shows why devices that keep trucks from accelerating above a certain level for what is likely to be a short distance isn’t a good idea.

Such a plan would increase the frequency of speed variance conflicts between big trucks and light-duty vehicles. Although multi-lane freeways safely deal with significant speed variances as long as the flow is not congested, conflicts increase when one truck is passing another with a speed differential of one-half mph, effectively blocking two lanes.

Drivers in states near Ontario, Canada, where many trucks are limited to 105 kph — or about 65 mph — have firsthand experience with congestion created by such a policy. Here’s what happens:  A truck in the right lane is traveling at 64 mph when a trailing rig decides to move to the left lane to pass.  But the trailing truck is limited to just 65 mph hour and can’t get the momentum needed to complete the maneuver quickly. This can create a rolling roadblock that takes a mile to resolve.

Once you get that type of congestion, bad behavior typical of frustrated light-duty vehicle drivers tailgating and lane bobbing proliferates in the backup. Speed limiters would spark a nationwide explosion in that type of driving.

The safety problem will be even worse on two-lane highways, particularly in states where light-duty vehicles can legally travel at speeds above whatever arbitrary top pace is selected for trucks. Multiple trucks will stack up in convoys running close together at the limit speed.  A three-truck convoy will be well over 200 feet long and a five-truck convoy could be more than 400 feet long. This will create extremely dangerous situations for light-duty vehicles attempting to use the oncoming lane for long distances to pass convoys of trucks that are packed together because their speed is electronically limited.

Limiters would have the effect of requiring differential speed limits for trucks in the many states that never had them, or which removed them after finding differential limits to be neutral or negative to safety.  Research sponsored by the AAA Foundation for Traffic Safety by Nicholas Garber of the University of Virginia found no safety value for differential speed limits for trucks..

Truck speed limiters would wrongfully re-impose federal control over speed limits that correctly belong to the individual states to suit their particular conditions.  Recent statements from some trucking groups seem to say they want to roll the clock back to 1987 to reinstate the hated and counterproductive 65 mph National maximum speed limit. There would be serious opposition to such a federal overreach.

The vast majority of goods we purchase travel in trucks. They account for 70 percent of all the freight tonnage moved in the U.S., according to the American Trucking Associations. That’s about 10 billion tons of freight. Requiring speed limiters will increase the costs of shipping in every state where the arbitrary limiter speed is below the current actual travel speeds for trucks.  The rule would also require more trucks on the road to carry the same number of ton-miles of freight. This will damage the economy and raise prices for everyone.

And there is no evidence that electronically limiting truck speeds improves safety. The Federal Motor Carrier Safety Association reported that about 80 percent of the fatal crashes with large trucks occurred in areas with speed limits no higher than 65 mph, and nearly 60 percent occurred in regions that have speed limits of 55 mph or lower.  Speed often is not the critical issue for fatal crashes with heavy trucks or any other vehicles, regardless of the posted limit. Speed as the principal cause for crashes almost never measures more than 6 percent or 7 percent of the total in unbiased research, and sometimes as low as 2 percent

A smooth and natural traffic flow is far more important than the absolute speeds, and truck speed limiters create a hurdle to achieving an optimum traffic flow.  Having trucks proceed at speeds closer to the light-duty vehicles is more important for safety.  And drivers with even a moderate amount of experience also know that sometimes the correct action to avoid a crash or another hazard is to temporarily accelerate. Speed limiters will take away this sometimes critical safety choice from truck drivers.

In reality, the speed limiter proposal was requested primarily by some large trucking firms to reduce some of the competitive advantages independent truckers and small firms often have over large carriers.

Independents and small firms already have a better safety record than large carriers, so safety was not the reason for the proposal from the large trucking firms. It would be totally wrong for the NHTSA and the FMCSA to adopt a rule to financially favor the large trucking firms at the expense of the more efficient independents that are also safer overall.

The federal proposal to require truck speed limiters should be rejected.


Source: Trucks

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