Do you employ drivers who suddenly get a lead foot once they are o at on the freeway? Or leave the engine running for 20 minutes while they grab a sandwich and a cup of coffee? You can disabuse employees of wasteful driving habits by outfitting company vehicles with a tachograph. The device records speed, fuel consumption, starts, stops, and idling time on small charts that are removable for review at the end of a single trip or workday.

Tachographs, sold by instrumentation companies, come in two types. Cable-driven mechanical units cost an average $280; newer electronic units cost an average $650. Both models perform essentially the same functions, except that electronic versions endure less wear-and-tear and are consequently more accurate and reliable. The units take about an hour to install and are put in place of the speedometer or tachometer. Charts are sold separately in boxes of 100 for about $7.85.

Island Transportation Corp., a $20-million trucking company based in Long Island, N.Y., orders a mechanical tachograph with each of its 175 Mack trucks. The devices come from Engler Vehicle Management Services Inc., of Jersey City, N.J. A supervisor reviews every chart at the end of the day to make sure drivers have obeyed the speed limit and remained on assigned routes. Charts that indicate excessive speed or travel distance are passed on to a safety director who disciplines the offending driver.

"The tachographs keep our drivers honest," says Raymond Bedford, Island Transportation's general superintendent of maintenance. He says the devices save a substantial amount of money in fuel costs, reduce the need for maintenance, and help prevent accidents.