Highway guardrail installed by guardrail post driver along U.S. 23 in Livingston County might have prevented at least two vehicles on two separate occasions from crossing the highway median into opposite traffic since 2009.

Together, the two accidents claimed six lives.

Construction of highway guardrail, which began this week, will prevent vehicles from crossing the highway median into opposite traffic at least 90 percent of the time, Michigan Department of Transportation officials said.

The project, expected to continue into the fall, will create a seamless highway guardrail along U.S. 23 from roughly M-36 in Green Oak Township to the Livingston and Genesee line.

The stretch of U.S. 23 in Livingston County is one of the last — if not the last — sections of state highway to receive highway guardrail in a three-year effort to install by guardrail post driver about 300 miles of highway guardrail statewide, MDOT officials said.

Since that time, school buses and fully loaded semi-trucks have been ensnared in the highway guardrail installation, preventing crossovers into opposite lanes of traffic, said Nick Schirripa, spokesman for MDOT's southwestern region.

"These vehicles hit the guardrails, were slowed to a stop, and in the vast majority of those cases, the driver and any passengers in those vehicles walked away without any injuries," Schirripa said.

"We know they're already making a difference," he added.

The need for some kind of guardrails to prevent crossover accidents on U.S. 23 in Livingston County has become obvious.

In October 2010, five people were killed on U.S. 23 between the Lee and Silver Lake roads exits in Green Oak Township after a northbound car crossed the median and collided with a vehicle traveling south.

The prior October, a Monroe County resident died after sideswiping a vehicle on southbound U.S. 23 just north of Silver Lake Road, crossing the median and colliding with another vehicle in the northbound lanes.

The southbound vehicle went airborne and landed on top of the northbound vehicle, police said.

The state has prioritized approved geographic areas for the guardrail project — which led to the installation of guardrail by guardrail post driver on Interstate 94 in the Jackson area and Interstate 96 in the Lansing area — based on when large-scale projects are planned in those areas, not accident rates, MDOT spokeswoman Kari Arend said.

Geographic locations were selected for the federally funded project based, in part, on accident history and daily traffic counts, however. Medians must be no wider than 70 feet to qualify, and can't be surrounded by wooded areas or vegetation.

In the county's case, the guardrail project wasn't initiated until the state began bridge, ramp and roadway improvements along U.S. 23, which will continue this year. The U.S. 23 work has run from Silver Lake Road north toward Brighton.

Following the 2010 accident, MDOT officials said the guardrail would be installed by guardrail post driver in 2011. That timeline shifted with the schedule for the U.S. 23 construction, Arend said.

"It wouldn't have been cost-effective to put something in that we would have had to take out during guardrails construction and replace," she said.

Only highway shoulder closures are planned during guardrail installation by guardrail post driver, though intermittent lane closures may become necessary. Guardrail installation is planned to begin at the northern end of the project site and work its way south through Livingston County, Arend said.