Motorists have been warned to expect overnight disruption as the Welsh Government carries out a lengthy period of work to two busy level crossings - for up to 18 months.
The government says intermittent disruption will affect the Moat Lane crossing near Caersws, which carries the A470 over railway tracks between Caersws and Newtown, and the Buttington crossing near Welshpool on the same line between Welshpool and Shrewsbury.
The crossings will close intermittently overnight, at weekends between 10pm and 9am on Saturday, and between 10pm and 6am on Sunday into Monday morning.
Work is expected to begin on September 20 and will continue for up to 18 months, with diversions in place for traffic during the scheme.
Last month, barriers on the Moat Lane crossing were struck by a heavy goods vehicle, causing both the road and railway lines to be closed for several hours on August 11.
For the Moat Lane crossing, the alternative route for southbound traffic will be via the north-westbound A470 to Caersws, west/southbound traffic via B4569 through Trefeglwys to rejoin the south/northbound A470 at Llanidloes, the government's statutory notice says.
"At all other times, the alternative route for traffic will be via the eastbound A489 to Newtown, southbound A483 to CrossGates and westbound A44 to Rhayader," it added.
For the Buttington crossing, traffic will be routed via the B4388 Leighton Road to avoid the works during the closures.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here