DALLAS -- Dallas City Hall is considering a plan to replace gas tanks on Ford Crown Victoria police cars with natural gas, but many police officers and their unions say that is a lousy plan.

City Hall said federal money would pay most of the $2 million cost to switch a group of patrol cars to natural gas instead of gasoline. The city has been waging a battle with Ford lately over the safety of these cars, and supporters believe the switch would boost safety.

In a city lot, 198 Crown Victorias are waiting to be put in service as new police cars. The city's plan calls for replacing these cars' gasoline tanks with five compressed natural gas tanks to reduce air pollution.

"If we can take 200 Crown Victorias and convert them to natural gas, which is much better for the environment, I think that's a good thing," said Dallas Mayor Laura Miller.

The city is suing Ford over the death of Officer Patrick Metzler (pictured) last October in a rear-end collision that triggered a gas-tank explosion, one of several such accidents around the country. Ford denies the cars are unsafe.

And while the city claims natural gas conversion would improve safety, the Dallas Police Association says it would reduce performance.

"None of them have been tested in Dallas, Texas," said Glenn White of the DPA. "Patrol officers haven't driven these cars, yet they're going to spend $1.9 million of the taxpayers money coming out of Washington, with 20 percent of that being supplemented through the city of Dallas budget. Total waste of money."

City papers said the conversion has been tested elsewhere. The city attorney who has been waging the battle with Ford refused to discuss the conversion plan.

"Overall, we think, the performance will be consistent," Miller said. "We think it will be better for the atmosphere. And I'm concerned personally about the Crown Vics in general, so, if we can make them safer, which I think there's a potential to do, that's a good thing, too."

The Dallas City Council delayed the discussion without comment Wednesday, as the staff works out the details. The federal money to implement the plan expires soon.