FMCSA speed limiter proposal leans on trucks' ECU

The engine control unit (ECU) might be the most critical component to the truck's power plant. 

Leaning on datafeeds from a network of various sensors, the ECU manages everything from the mixture of air and fuel to idle speeds and valve control and timing, and it soon could be a key piece of regulatory compliance. 

The Federal Motor Carrier Safety Administration’s (FMCSA) notice of intent to proceed with rulemaking to mandate speed limiters on most heavy-duty trucks published in the Federal Register Wednesday, May 4, restarting a process that had been dormant for six years. At the time the 2016 Notice of Proposed Rulemaking (NPRM) was published, NHTSA and FMCSA stated that all vehicles with ECUs are generally electronically speed governed to prevent engine or other damage to the vehicle. Since the ECU monitors an engine’s RPM – from which vehicle speed can be calculated – it also controls the supply of fuel to the engine. 

[Related: Most fleets already use speed limiters]

"Based on this background, it is likely the required means of achieving compliance with a speed limiter requirement would be to use the ECU to govern the speed of the vehicle rather than installing a mechanical means of doing so," FMCSA wrote in its notice last week. 

FMCSA said it intends to issue a supplemental notice of proposed rulemaking that would, if adopted, "impose speed limitations on certain CMVs subject to the FMCSRs. The rulemaking would propose that motor carriers operating certain commercial motor vehicles, as defined in 49 CFR 390.5, in interstate commerce that are equipped with an ECU capable of setting speed limits be required to limit the CMV to a speed to be determined by the rulemaking and to maintain that limit for the service life of the vehicle."

A poll conducted by CCJ earlier this week showed that a majority of responding motor carriers already have speed limiters deployed on their trucks.

Navistar Vice President of Engineering Darren Gosbee noted fleet customers already have the ability to include speed governor parameters into their truck specification when they order a vehicle – "parameters that are programmed through the vehicle engine’s ECU," he said. 

"When it comes to implementing a speed limit in heavy duty trucks, most OEM’s already have a version of this functionality to support most fleets," added Johan Agebrand, director of product marketing, Volvo Trucks North America. "This is usually implemented in the vehicle ECU or engine ECU, or combination of both. The implementation is not the most important discussion point, however; rather, the question is will the proposed regulation actually achieve what it is intended to do."

Agebrand expressed concern that speed limiters could have negative safety implications by increasing speed differentials between trucks and passenger cars and could drag down truck driver pay by reducing miles driven under their hours of service.

Neither the 2016 proposal nor last week's notice set a maximum limited speed. However, the Department of Transportation in 2016 appeared to be leaning toward 60 mph, 65 mph and 68 mph based on analysis on those speeds released within the rule at the time.

If a fleet tractor doesn't roll off the assembly line with a governed speed, or the speed limit needs to be changed, Gosbee said that likely means a call for service. 

"An update to speed governor parameters would require a visit to a dealer service center," he said. "Depending on the vehicle, an over-the-air update to adjust the speed governor parameters can also be completed."

Agebrand echoed those sentiments, adding that if speed limiter requirements on commercial trucks become a rule, Volvo Trucks customers "can be confident its trucks will be reprogrammable to support it. For all Volvo trucks model year 2018 and newer, this can even be done through remote programming service, the VTNA over-the-air solution," he added. 

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