SULLIVAN — As part of the ongoing reconstruction of Route 9 in Roxbury and Sullivan, the N.H. Department of Transportation has announced a seven-month regional truck detour slated to start at the beginning of April.

The detour, which will use Routes 202 and 101, will be in effect during the replacement of the Route 9 bridge over Otter Brook in Sullivan. A local alternative is planned for smaller cars and trucks, but employs a sharp turn and a narrow stretch of road not suitable for larger vehicles, according to a news release from the state agency.

The seven-month truck detour — which will also be for large motor homes and vehicles with big travel trailers — will bring motorists heading west on Route 9 onto Route 202 in Hillsboro, then to Route 101 in Peterborough to continue west to Keene. Eastbound vehicles will be detoured to Route 101 in Keene, then to Route 202 in Peterborough and onto Route 9 in Hillsboro.

The bridge replacement is part of the ongoing, $13.5 million Route 9 reconstruction project, from the area near Granite Gorge Ski Area in Roxbury to the intersection with Centre Street in Sullivan, according to the news release. The work also includes slope reduction, tree removal, drainage and guardrail upgrades and the rehabilitation of the Centre Street Bridge.

The project’s completion date is July 24, 2020.