A multi-million pound bypass, planned for 70 years, officially opened on Thursday in Powys.
One carrier said the Newtown bypass would make a "big difference" because of 45-minute delays in the city, while the local AM representative said the day was "memorable".
The Welsh government said the road would alleviate traffic jams of about 40% in the city center.
A public notice printed in 1949 indicates that a bypass bridge was under study by the former Montgomeryshire County Council.
The six-kilometer (6.4 km) route heads south of the city with two lanes in one direction and one in the opposite direction to provide passing points.
For many people in the area, it is extremely important.
Colin Owen, who runs the RA Owen and Sons coal and agriculture merchants in the nearby town of Llandinam, said Newtown was dubbed the "Central Wales Car Park" because of the long delays in traffic .
"People were afraid to go to town because they did not want to get out of the queue of traffic because they would only have to join her again ", did he declare.
"It's going to make a big difference, and it will ease the flow and save us a lot of time across Newtown."
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Joy Hamer, 86, a long-time resident on the main road, said traffic problems have long been an important part of local life.
"It will be a big deal for the city," she added.
Newtown Mayor Sue Newham said, "A new chapter has been launched for our city and we intend to make the most of all opportunities."
And Ed Humphreys, a city council member, said, "Change is the lifeblood of opportunities for Newtown."
The bypass is open less than three years after work began on the £ 95 million project. But the road was long.
Why the holdup?
A public notice issued in August 1949 asked "schoolchildren aged 16 or over" to work as investigators to count the vehicles used for a traffic investigation.
There were also discussions about a bypass in the 1960s and 1980s, but the go-ahead never came, as many had a mixed reaction to the idea.
In recent years, congestion around the city has worsened, a situation mainly attributed to traffic lights replacing a roundabout.
And people have expressed frustration, including saying that traffic is driving buyers away.
Increasing congestion has brought about a change in public opinion, according to AM Russell George, Montgomeryshire's conservative.
The Welsh government said Newtown's industrial development had been "hampered by congestion problems".
Then, in 2008, he confirmed that he would finance the project and work was to begin in 2011.
But it was put on hold after an expenditure review in 2010.
In 2011, Mr. George presented the ministers with a petition with 10,000 names to begin work.
And construction began in March 2016, although after a further delay, although contractors have delivered the project in advance.
Mr. George stated that the opening of the bypass was a "memorable occasion".
The launch will be made by Ken Skates, Minister of Transportation and Economy, who said it would "reduce travel times and improve air quality in the region".