EVINGTON, Va. — A new device is being touted as a convenient and reliable way to keep Type A school buses from speeding, potentially increasing safety and fuel economy.

InterMotive’s Speed Sentinel II, a micro processor-controlled unit for Ford and GM chassis, can be programmed to limit the speed of a bus without limiting the engine.

“Wherever you have it set — maybe 70 — if you need to accelerate to merge onto a freeway, you have full engine output,” said Marc Ellison, InterMotive’s vice president of sales and marketing. “When you reach 70, it sends a signal to the processor. The pedal can go all the way to the floor, but the vehicle won’t go faster.”

On newer Type C and D school buses, this type of speed control is a programmable feature in the engine software. Type A buses don’t have that feature, but there is at least one aftermarket speed limiter that has been available for some time.

But Brady Childress, director of customer support for Virginia bus dealer Sonny Merryman Inc., said that product hasn’t done well in keeping up with engine software, resulting in recurring “check engine” lights. “It’s also a pretty large device and is labor intensive to install,” Childress said.

InterMotive’s product, on the other hand, is compact and uses “plug and play” connectors that plug directly into the vehicle’s OEM connectors. This approach reduces the installation time and improves connection reliability.

Ellison said that easy adjustability is one of the key advantages of Speed Sentinel II. (As a side note, Speed Sentinel I was targeted at the emergency response vehicle, taxi and work truck markets but not the school bus market.)

There are two ways to change the speed setting: One is to remove the lid of the module, which is mounted under the dash, and turn a dial. This method takes less than a minute and allows the maximum speed to be set in 5 mph increments from 10 to 80.

The other way is to hook a computer up to the module, which allows the maximum speed to be set in 1 mph increments. This can be done in about two minutes.

Speed Sentinel II has an optional passing mode that allows for a 10-second override of the programmed speed limit. Also, since the device doesn’t affect brakes, a vehicle could exceed the set speed when going downhill.

Sonny Merryman Inc. has already installed Speed Sentinel II on a few buses, and Childress said that the device has gotten good responses so far.

“We’re very impressed with the product,” Childress said. “It has done everything InterMotive said it would do.”