Kansas City, Mo. ? By early next spring, drivers on the interstates that surround Kansas City will know about how long they are going to be sitting behind a traffic accident or construction slowdown.

Improvements to the Kansas City Scout traffic management system will make the area one of 26 cities across the country able to give motorists travel times, the Federal Highway Administration said.

The large message boards over the interstate currently warn motorists about lane closures, crashes and construction but give no hint of how bad the backup may be.

“Right now, it’s purely guesswork,” said Kirk Herring, of Overland Park. “You can’t tell whether you should jump off the highway or not.”

Engineers at Kansas City Scout, which runs the message boards along with 90 traffic cameras, are installing the time software this month, at a cost of $240,000.

Other improvements also are planned, including allowing drivers to get e-mail traffic alerts for their customized routes. Drivers also can sign up for text-message alerts on their cell phones, pagers or BlackBerries.

The system also will add more cameras next year, extending its reach to parts of Lenexa, Lee’s Summit and Olathe. And a full complement of cameras, message boards and roadway sensors will be added to Interstate 635 in Kansas City, Kan.

Kansas City Scout, a $40 million system operated by the transportation departments in Kansas and Missouri, covers 90 miles of interstate, with 37 message boards around the metropolitan area.

Jerry Jones, of Kansas City, said he doesn’t count on the signs for much information now, but he would pay attention to travel times.

“I just need to know how long I’m going to be in the car and how long am I going to be obstructed from getting from point A to point B,” Jones said.

The travel times will be calculated by determining vehicle speeds from sensors embedded in the interstate pavement. But broken sensors can skew the calculations, which has caused problems in other cities.

Kansas City officials say they will stop posting travel times at certain locations if the sensors aren’t functioning. And they will do extensive studies to verify the system’s accuracy before launching the program.

“We realize when this becomes available it probably will be very popular,” said Mark Sommerhauser, a project manager for Scout. “A lot of people will want it, and they’ll want it every day. It will be unacceptable if we put on the sign that travel times are unavailable today.”