The average age of new buyers of Town Cars, which is 67, does not reflect the many bought by fleet operators.

A breakthrough on the government side, he said, occurred when Texas voted to give financial incentives to fleet operators to switch to natural gas.

Commercial fleet operators commonly aim their trucks' headlights slightly downward, although that is not required by regulations.

Mr. Rozint said he expected the first systems to be installed by fleet operators.

It is sold to manufacturers of locomotives and to fleet operators.

The big fleet operators get the biggest discounts - putting the dealers under pressure to maintain higher prices for private buyers.

Commercial fleet operators also need to be able to confirm proof of delivery of goods to their customers.

The United Parcel Service is the first such fleet operator to take advantage of this offering.

In Texas and other places where local gas utilities have been aggressive, some fleet operators are converting.

The first of the fleet operators began services in 2005, with increasing numbers of companies starting operations in 2006 and 2007.