JEFFERSON CITY, Mo. -- For years, transportation planners have talked about the potential benefits of separating cars from trucks on the nations highways.

More recently, proposals to create "truck-only lanes" have gained ground as government agencies and others look not only at improving safety but also at how to cope with projected increases in traffic and how to more efficiently move vehicles.

Except for a few such lanes for short distances in New Jersey, California and Texas, nothing large-scale has been implemented.

Now, however, the Missouri Department of Transportation is discussing the potential of designated over-the-road truck and bus lanes on Interstate 70 across Missouri.

A study charged with exploring needed long-term improvements to I-70 recently recommended the state add four truck/bus-only lanes to the stretch between Kansas City and St. Louis as the best option.

The proposal calls for construction of two truck/bus lanes and two or more general-purpose lanes in each direction along the existing I-70 highway. The truck/bus lanes would be separated from general-purpose lanes with concrete barriers or grassed areas.

"We have talked to very few people who dont like the idea," Bob Brendel, the Missouri Department of Transportations project manager for the I-70 study, told a Missouri newspaper.

Missouri began weighing the idea several years ago, Brendel said, as it started looking at how to address projected increases in traffic volume on I-70.

The cost of a truck/bus option is formidable: Up to $4 billion, according to the study. That compares with a cost of up to $3.5 billion to rebuild and widen I-70 to six lanes, although the truck/bus option would mean a total of eight lanes all along I-70.

"Its a big-ticket item no matter how you do it," Brendel said.

Meanwhile, MoDOT is applying for a $200 million federal grant to build up to 30 miles of truck/bus-only lanes on the stretch of I-70 running through Saline and Cooper counties in the middle of the state.

If approved, that pilot project would give planners an idea of how truck/bus lanes would work, says Brendel.