The federal government's cash-for-clunkers program caused a stir this weekend with many consumers heading out to auto dealers' showrooms to trade in their car, with many concerns now surfacing about how the program really works and how long it will last.

The cash for clunkers program, officially called the Car Allowance Rebate System, took effect July 1, and rules were published Friday. The program provides vouchers ranging from $3,500 to $4,500 as an incentive for consumers to turn in older vehicles to buy more fuel-efficient cars from participating dealers. The government reimburses dealers.

It runs through Nov. 1 or when the $1 billion that Congress allotted runs out.

The 136-page outline of the plan includes detailed regulations -- especially when it comes to the process of disabling the engines of the old vehicles.

Nationwide, an estimated 250,000 people could get credits, helping to boost sales at a time when industry sales are down 35 percent.

The government has launched a site: which offers more information which consumers can check out before going to the auto dealers.