The new state law that bans smoking in public places beginning today doesn't mean people will quit tossing cigarettes butts in public places.

There may be no better proof than the Liberty Tunnels, arguably Pittsburgh's biggest outdoor ashtray.

On every shift, Pennsylvania Department of Transportation tunnel workers use a hand-powered device -- they call it a "butt sweeper" -- to pick up butts around both portals.

"If we didn't, this place would be flooded with cigarette butts in a few days," assistant tunnel superintendent Joe Thomas said, standing outside the Liberty Tunnels maintenance quarters. "Instead of using an ashtray, people flick 'em out their window. If we didn't keep this place clean, they'd be screaming."

Mr. Thomas acknowledged that some newer cars don't have ashtrays, but he also pointed out that motorists can buy ashtrays made to fit inside cupholders.

More than 75,000 vehicles a day travel the 1.1-mile-long tunnels, a lifeline between the city and the South Hills.

Signals at both ends result in stop-and-go traffic and, often, long, slow queues. As a result, many smokers light up inside the tunnel, and when they're finished, they throw the butts out the window.

Large fans used to blow motor-vehicle exhaust fumes out of the tunnel also sweep some of the butts outside.

Other butts roll down Saw Mill Run and West Liberty Avenue ramps at the southern end, collecting at the bottom at the curbs or around traffic islands. The same thing happens at the McArdle Roadway-Liberty Bridge intersection.

While tossing cigarette butts on public property constitutes littering and could be subject to a fine, police rarely, if ever, enforce the law.

So many cigarettes accumulate in drains inside the tunnels that the grates have to be removed at least once a year and the butts have to be sucked out by a truck-mounted vacuum. The annual butt cleaning costs PennDOT about $6,000.

Tunnel workers fear that the new statewide smoking ban could exacerbate the butt problem at the Liberty Tunnels and other places, because people will be anxious to get that first or last puff, depending on whether they're coming or going to where smoking is banned.

Port Authority officials said they didn't know for certain whether the smoking ban applies to transit stops and transit shelters, where strewn cigarettes also create a mess.

"Our interpretation is that the smoking ban pertains to inside places," spokesman David Whipkey said.