Controversial plans by energy companies to transport huge wind turbine blades and towers through a small Powys town have been rejected.
People in Montgomery had campaigned against large trucks travelling through their streets.
The decision was made after Powys council asked companies to "clearly demonstrate" they could reach their planned wind farms sites.
When they were unable to do this, the Montgomery route was deemed "unviable".
Last year, a report warned that "significant disruption" could be caused to communities by taking turbines by road.
Lorries towing extended trailers have been carrying out a number of test runs in south, mid and north Wales this year.
The trials are simulating the sort of impact wind farm traffic could have on roads and communities.
A Powys council spokesman said: "The Welsh Assembly Government and ourselves have asked each of the wind farm companies wishing to build in Powys to clearly demonstrate that they can actually get to the sites they have proposed.
"However, we will not allow every road in Powys to be used because of the impact these proposed developments will have on the northern part of the county."
The council said a strategic approach had been agreed with police and the assembly government to manage the impact of wind farm traffic.
"A northern route for the Llandinam wind farm which would have taken wind farm components through a historic county town (Montgomery) and into Shropshire had been proposed by ScottishPower but there were constraints along this route," said the spokesman.
"Unfortunately, no solutions were proposed that addressed these constraints, making the route unviable."
The spokesman said ScottishPower had decided to look at an alternative route from the south which goes into Herefordshire.
Montgomery's mayor Cerys Thomas welcomed the decision.
"People in the town are very pleased, especially those living along the route," she said.
"We were concerned because we thought it wouldn't just be lorries carrying turbines and blades coming through Montgomery, but ancillary traffic such as cement lorries and diggers."
The assembly government said it was working with the wind farm industry, local authorities, highway bodies and the police on ways of bringing wind turbines safely to sites, while reducing the impact on communities, businesses, the environment, and traffic.
A spokesman added: "General principles for the movement of wind turbines to minimise disruption to local businesses are being drawn up for discussion."
A report for Powys council by consultants Capita Symonds last year, highlighted the logistical problems of transporting a new generation of larger, more powerful turbines to the uplands of mid Wales.
It said narrow country roads would have difficulty coping with the trucks needed for the structures, some standing at 400ft (122m).