Three highway work-zone crashes overnight sent three people to hospitals.

Construction workers are vulnerable and must work in dangerous settings. Highway construction sites have limited protection options, and workers are almost totally dependent on drivers paying attention.

"So it's really about active construction, changing conditions, closed lanes and really paying attention to what's happening out there," State Highway Administrator Gregory Slater said. "If you just slow down a little bit as you go past them, it makes them feel safer and (makes you) be safer at the same time."

Just after 1 a.m. Friday, a car slammed into a truck carrying construction equipment as it slowed to enter a highway work zone on the Beltway near Harford Road. The injured driver is being treated at Sinai Hospital.

Shortly after 2:30 a.m., on the Outer Loop of the Beltway at Providence Road, two cars collided while trying to merge into lanes that are reduced because of construction. One driver is being treated at MedStar Franklin Square Medical Center.

About a half hour later, again at the Harford Road construction zone area, and despite a parked state trooper vehicle with emergency lights flashing, a sport utility vehicle plowed into the back of a parked pickup truck, pushing the vehicle into two workers who were on foot. The workers are being treated at Shock Trauma. The driver was taken to the University of Maryland St. Joseph Medical Center. Police say neither alcohol nor drugs is a factor.

"In all those incidents, there were people that didn't quite merge, or they went into the work zone or into a closed lane and caused the crash," Slater said.

Maryland's "Move Over" law, passed by the General Assembly in 2010, requires drivers, if possible, to move a lane away from roadside emergencies and roadwork crews.

"I can speak from experience that when you are standing on the shoulder or the median and trucks drive by and cars drive by you, you feel that. You get a little bit of a shake, or you feel your car move or yourself move," Slater said.

The State Highway Administration is frequently putting enforced barriers around work sites, among other things.

"We have these attenuator trucks on work zones, you may have seen them, on the side of the road. What they are is a truck that's pulling a trailer that has a cushion-type of situation. So what that does, as those workers are on the side of the road, that gives them a buffer and protects them from that traffic going by," Slater said.

Six people died in Maryland highway work-zone crashes last year, and one has died so far this year.

According to SHA officials, this is the largest construction season in Maryland history.