For the past year, drivers on a stretch of Florida's Turnpike have paid their tolls electronically — without having to slow their cars to a stop.

The conversion to electronic collections in Miami-Dade County reflects a growing trend among U.S. toll road operators toward open-road — or cashless — collections. It's a model that toll-road proponents want to follow on a stretch of Interstate 70 through mid-Missouri.

Instead of rolling up to a toll booth and reaching for a wallet, drivers on these tollways pass beneath a gantry that may be outfitted with cameras, lasers and devices that read transponders or tags inside the passing vehicles.

"The trend is toward cashless toll roads," said Neil Gray of the International Bridge, Tunnel and Turnpike Association.

Missouri state Sen. Mike Kehoe, R-Jefferson City, last week introduced a public-private partnership bill that would turn I-70 into a toll road whose operator could "use any method for collecting and enforcing user fees."

Those measures, according to Senate Bill 752, may include billing accounts, commuter passes, and electronic recording or identification devices.

Missouri Department of Transportation officials say the conversion of I-70 to a toll road would allow the state to add lanes to a nearly 200-mile stretch of the highway at a cost of $1.5 billion to $4 billion. The project would be undertaken by a private consortium. Private companies would finance, rebuild and operate the highway.

MoDOT Director Kevin Keith and others have stressed that the toll road would use an open-road toll system rather than toll booths, which cause traffic to stop.

"If you can get that part of it through to people, they go from totally hating it to just disliking it," quipped Kehoe, a former state highway commissioner and vice chairman of the Senate Transportation Committee.

Missouri first envisioned electronic toll collections in 2001 as part of an environmental study of rebuilding I-70. Under one of the scenarios, MoDOT considered building a parallel toll road next to the interstate.

It would have used traditional toll plazas but set aside exclusive lanes for drivers whose cars were outfitted with transponders so drivers could be billed.

Under the latest proposal, all of the lanes of rebuilt I-70 would likely pass beneath toll gantries equipped with devices that communicate with tags in passing cars or take pictures of license plates to bill registered owners.

The gantries, Kehoe said, would be "literally invisible to the traveling public."

Last February, Florida's Turnpike Enterprise converted a stretch of that state's turnpike into an all-electronic toll system.

Florida transportation leaders viewed it as a safety improvement. Traffic backs up at the traditional toll plazas while others using the SunPass system had their own lane and did not stop. The potential for accidents is greater with the toll plazas.

So far on the all-electronic segment, there has been a 76 percent drop in accidents, said Sonyha Rodriguez-Miller, a spokeswoman for the Florida enterprise.

In North Carolina, the state opened a new toll road in December that uses electronic tolling. Drivers on the Triangle Expressway in the Raleigh-Durham area can set up a Quick Pass account to pay their tolls electronically.

If not, the registered owner of the car is mailed a bill but — as with other electronic toll systems — the owner is charged more to cover the cost.

The North Carolina Turnpike Authority hoped to sell 2,400 Quick Pass transponders by June and has already sold 13,000, said Reid Simons, a spokeswoman for the turnpike authority.

The North Texas Tollway Authority converted the Dallas North Tollway to cashless tolling in December 2010. The state touted the move as a way to alleviate congestion, improve safety and boost air quality by reducing vehicle idling.

But convenience store owners along I-70 in Missouri worry drivers will avoid their businesses if the electronic toll plazas are located near their exits, said Ron Leone, Executive Director of the Missouri Petroleum Marketers & Convenience Store Association.

Statistics show a bloc of drivers — at least 10 percent — will divert to free highways to avoid a toll road and that would be a blow to businesses, Leone said.

"There are a dozen reasons we think this is a bad idea," he added.

Opponents of using tolls to rebuild I-70 say the concept should go to a public vote.

Kehoe's bill has no provision for a statewide vote. Missouri transportation officials and others contend that under the narrow circumstances of forming a public-private partnership to rebuild I-70, a public vote does not appear to be required.

Proponents add that the Legislature previously passed a bill that would have enabled the state to enter into a public-private partnership to build a new Mississippi River bridge using tolls. That bill also was signed by the governor.

But in a potential blow to those hopes, the Missouri House last week passed a bill proposing to bar the construction and operation of future toll roads. The bill's sponsor, state Rep. Thomas Long, R-Battlefield, did not return a phone call seeking comment.