Don't be too alarmed to see stepped-up security on MetroLink or Amtrak trains in St. Louis.

During the past week or so, Metro and Amtrak officials have alerted their passengers that they may encounter canine teams and uniformed law enforcement officers.

"This is not in response to any sort of threat or risk," Amtrak spokesman Marc Magliari said last weekend. "This is something we are doing around the country more and more. I think our customers are going to see this more and more often as they travel around our system."

The surge team was in St. Louis for an undisclosed number of days, Magliari said last Sunday. The dogs are brought in to detect explosives on arriving and departing Amtrak trains.

This stepped-up security corresponds with the holiday weekend — a time when more people are out and about. Metro is expecting big crowds this weekend and will have extra trains for people attending Fair St. Louis.

This weekend, Metro — along with the U.S. Department of Homeland Security and local police agencies — will patrol the transit system. The operation goes by a clunky name: Visible Intermodal Protection and Response. And this weekend isn't the first time it has been in effect. The teams are on the system a few times a year.

"Metro, local and federal law enforcement agencies participate in an ongoing cooperative effort to make sure that law enforcement and first responders are prepared to protect transit commuters," said Metro Chief Willie McCuller.

Metro officials wanted people to know the teams are out this weekend.

Again, there is no specific threat targeting passenger rail or public transportation, officials from the two agencies said. But there is no denying that crowded trains and buses have been targeted by terrorists in the United States and abroad.

Unlike airports, people boarding passenger trains and light-rail vehicles are not forced to pass through a magnetometer or face explosive-detection measures.

"None of the surface-transportation modes have it," Magliari said. "This is an open system. It always has been. Unlike aviation, which tends to work from staffed location to staffed location, not every location is staffed. Not every bus stop is staffed. Not every train stop is staffed."

Lane closures take a Holiday

The Missouri Department of Transportation said it will suspend lane closures until Tuesday in observance of Independence Day. But some downtown exits will be closed because this weekend for the Fair St. Louis parade and festivities.

Those include westbound Highway 40 (Interstate 64) to Market Street; eastbound Highway 40 to 20th Street/Chestnut; westbound Interstate 70 from the Poplar Street Bridge; northbound Interstate 55 to Memorial Drive; and northbound Memorial to westbound I-70, MoDOT officials said.

Other closures will include eastbound I-70 to southbound Memorial and eastbound Memorial to the Poplar Street Bridge.

Q. At the intersection of Creve Coeur Mill Road and Olive Boulevard, there are two lanes on Creve Coeur Mill — one for turning right and the other a left-turn lane. However, the light standard opposite Creve Coeur Mill has two banks of lights, each indicating a left arrow. It would appear that the right bank should be a right arrow, considering that's the only way to turn. I have seen cars turning from the right lane onto Olive.

— Jerry Goldberg

There are two left-turn signals directly in front of the single left-turn lane where southbound Creve Coeur Mill intersects with Olive. But because most traffic using that signal is turning left, the Missouri Department of Transportation said it is required to have two signals to indicate that turn.

MoDOT traffic engineers said there are actually three signals there — one in the median and two overhead. MoDOT spokesman Andrew Gates said the right-most overhead signal head "is probably not needed there." Gates said the state is looking at it. But in the meantime, motorists should not turn left from the right-hand lane on Creve Coeur Mill.

Q. Why does bridge concrete never seem to need resurfacing? We've observed that road resurfacing seems to start or end at the overpass. From this we infer that bridge concrete does not degrade as fast as road concrete. What is the truth?

— Jim Holstein, St. Peters

Bridge concrete does break down, but there are reasons you don't see some of the traditional resurfacing work you will find on local streets, said Mark Croarkin, MoDOT's local bridge engineer.

To resurface a concrete bridge, crews generally remove the existing concrete and replace it. Putting an additional layer on top of a bridge's existing driving surface can add more weight than a bridge is designed to handle. And certain overlays can trap moisture near the surface and damage steel in the bridge. Additional layers of concrete applied to a bridge driving surface are typically very thin.