Speed/rev limiters

Speed limiters have been a mandatory feature of goods vehicles over 3.5 tonnes and buses with more than eight seats for a number of years, but they have increasingly been introduced voluntarily on smaller vehicles by safety-focused company bosses.

Limiters are designed to prevent road crashes by stopping vehicles from going over the speed limit – or reaching it in some cases – by restricting the fuel supply to the engine.

The limiter restricts the maximum powered speed to 56mph for goods vehicles, and 62mph for buses.

Data from Northgate Vehicle Hire suggests that speed limiters not only improve road safety, but also deliver fuel cost and CO2 emission savings:

• Cutting speeds to 62mph on motorways reduces deaths by 46%.
• Driving at 60mph instead of 70mph delivers a 20% fuel bill saving.
• Limiting a vehicle to 62 mph delivers a 6-7% reduction in CO2 emissions.

Rev limiters are fitted to internal combustion engines to prevent maximum power being attained, thus reducing wear and tear, improving fuel efficiency and reducing vehicle emissions.

However, even more sophisticated technology is available.

BT is remapping the engines powering 23,000 of its commercial vehicles aiming to improve efficiency by changing vehicle characteristics including throttle, engine rpm, torque and speed, which in turn determines power output, MPG and CO2 emissions. (See Fleet News Awards profile, page 38).

Additionally, some organisations have launched engine power management systems.

Oxfordshire-based Zeta Automotive, for example, has developed Econospeed, a dynamic throttle controller that allows a vehicle’s maximum road speed, engine speed and maximum rate of acceleration to be limited to customer-defined criteria.

Business development manager Dougie Black said: “By electronically restricting a vehicle’s maximum rate of acceleration and forcing earlier gear changes by limiting maximum revs, Econospeed encourages economical and careful driving.”