Heads up, New Yorkers. You never know when your neighborhood sidewalk will turn into a construction detour for motorists.

A National Grid construction crew blocked Prospect Place between Flatbush Avenue and Sixth Avenue this morning. Since the crew failed to cork the street at the top of the block by Flatbush, drivers were expected to just figure it out once they had already turned down Prospect. Of course, some drivers took the most direct route possible: Jumping the curb and driving on the sidewalk with pedestrians.

Rob Underwood was walking home after taking his kids to P.S. 282 when he came across the scene. “It looked like one of the drivers had gotten out of his car to yell at the construction workers and then got back in his car to drive around on the sidewalk,” he said. Other drivers followed. One SUV driver almost got stuck, with the vehicle fenced in on the sidewalk by an old fire call box. At another point, a livery car driver idled on a curb ramp as a woman walking with a stroller and child tried to get by.

“After probably six cars tried to go through, cars tried to go out in reverse back to Flatbush, which is probably dangerous, but less dangerous than driving on the sidewalk,” Underwood said.

In September, DOT issued a street construction permit to a National Grid subsidiary for gas work on this block of Prospect Place. The permit expires on Sunday.

Update 12:45 p.m.: “As part of our ongoing gas main replacement program, National Grid is upgrading and installing about 200 feet of gas main and new service lines to homes for our customers on Prospect Place. We have appropriate permits from DOT allowing temporary traffic control devices to close the street periodically,” National Grid spokesperson Karen Young said in an e-mail. “Safety is our number one priority; we have a flagger onsite and proper barricades to close off the street as needed to complete work and protect the public and our workers. The barricade was breached this morning and we took immediate action to secure the area to ensure the safety of the community and our crews.”