Rain combined with earlier darkness has created treacherous conditions for motorists on Highway 101 between Geyserville and Windsor.

The highly touted resurfacing project known as the “Big Pave” along that stretch is underway, but as a midweek storm fell, the construction zone lacked lane lines or raised reflective markers to keep cars oriented and separated. The insufficient safety measures mixed with scant lighting created chaos, according to those who drove through it, nearly causing multiple accidents.

“Since they resurfaced it, they haven’t striped it very well,” said Chris Kates, a Cloverdale resident who said he barely avoided two collisions on the rain-slick roadway Wednesday night. “So all you’re really looking at is this big, black crevasse as you’re trying to drive 40 to 50 miles per hour.”

The frightful experience was shared by others in recent days. Those merging onto freeway on-ramps — in areas already known for their poor visibility at night — were reportedly confused by the lack of guiding lines, creating dangerous near-misses. Even one of biggest supporters of the long-awaited project was affected.

“It was very dark and challenging to delineate the lanes between Windsor and Healdsburg,” said state Sen. Mike McGuire, D-Healdsburg.

McGuire’s office received several calls from concerned drivers about the issue. By Thursday morning he was in touch with Caltrans to try and rectify the safety issue and crews were dispatched to work overnight installing lane delineators along the corridor.

RocQuel Johnson, a Caltrans spokeswoman, said Friday that construction, including the lane separators, continues on the north and southbound lanes. She said she believed the work, including installation of raised reflective markers, to be contingent on weather. The storm kept it from being completed immediately following the repaving, she said.

Caltrans crews were set to work overnight, 9 p.m. to 7 a.m., starting Friday and through the weekend, to remedy the problem and get reflective markers installed.

“They’re already in the works,” said Johnson. “But most of the projects in that time phase are weather-dependency projects, and it just depends on what the weatherman says and of course it fluctuates between who says what. So we’re hoping that the weather can clear up a little.”

Officer Jon Sloat, spokesman for the California Highway Patrol, said he didn’t know of an increase in vehicle crashes on the 18-mile stretch as a result of the lack of adequate safety measures. The new mitigation measures can’t come soon enough for anxious commuters.

“If they don’t do something about it, it’s going to continue to be an unsafe stretch of highway,” said Kates. “I can’t even imagine what it will be like when there’s torrential downpours.”

You can reach Staff Writer Kevin Fixler at 707-521-5336 or at kevin.fixler@pressdemocrat.com.