Q: As my work takes me around to some of the small towns and villages in the Quad-City area, I notice two signs upon entering a town. One always says, "Reduce speed ahead." I get that one. The other sign throws me for a loop. It says "Engine braking not allowed." I don't understand what that means. Any idea?

- Quad-Citian

A: The sign is targeted at the drivers of big rigs and a safety device that is commonly called a "Jake brake," according to Brenda Neville, president of the Iowa Motor Truck Association based in Des Moines.

The Jake brake is an add-on engine brake for diesel engines. "Big trucks that move virtually everything we use weigh as much as 80,000 pounds, so stopping them or slowing them down results in a great deal of wear and tear on the brakes, which are replaced frequently," Neville said. "The Jake brake is an engine brake, also know as a compression brake, which is used to slow down a large vehicle and extends the life of wheel brakes and offers substantial savings over the life of a truck."

The Jacobs Co. of Bloomfield, Conn., is credited with perfecting and marketing the device, thus the "Jake brake" nickname that developed over time. "It only has one drawback - it is very noisy," Neville said. "You may have heard a big truck use the Jake brake without realizing what it was. Sometimes when a truck is approaching a stop sign or stop light, it suddenly emits a loud roar, very much like a large lawn mower, for five or 10 seconds."

The noise is what's causing many towns and counties to ban the use of the Jake brake in those jurisdictions, she added. "Even though tests have shown the decibel level to be about as loud as a large lawn mower, at night or early morning, the low frequencies seem to carry a long distance and are very noticeable and may cause complaints by folks residing close to the roadway."

Neville said since the primary use of the Jake brake is to slow the truck on long downhill grades, the technology will continue to be widely adopted for use on the open road. "If an area has a number of long downhill grades, it may be of value to re-evaluate the purpose of the ban and determine if stopping the noise is of greater value than stopping a runaway truck."

Q: Are there plans to repaint the Interstate 74 bridges? They sure are looking bad.

- Quad-Citian

A: There are plans for repainting the bridges, said Doug Rick, Interstate 74 project manager for the Iowa Department of Transportation. The bridges will not be repainted in their entirety, but areas most susceptible to damage from winter salt will be painted. The painting originally was set for 2011 after the scheduled rehabilitation of the bridges in 2010. However, both projects likely will be pushed back one year because of the pending 2010 repair work on the Interstate 80 bridge, Rick said.