Calls have been made for safety measures along Western Avenue in Daventry.
The move comes after a car collided with an elderly pedestrian on the road on Sunday afternoon.
Northamptonshire Police said that at about 5.30pm close to the Orchard Street junction, a grey Vauxhall Corsa, being driven by a 62-year-old man, collided with a 92-year-old man who was on foot.
The pedestrian was seriously injured and taken to hospital in Coventry.
Police are asking anyone with information to call the Drivewatch Hotline on 0800 174615.
Anthony Gibbons was walking his dog along the road at the same time.
He said: “I got there a few minutes after it happened. I think the pedestrian must have been going to the shop because he had been carrying a carton of milk.
“The milk was all over the car and its windscreen was smashed.
“I didn’t see the collision happen, so I don’t know what caused it.”
But Mr Gibbons, who has lived by the road for two years, said something needs to be done to improve safety for motorists and pedestrians.
Western Avenue was originally built as the town’s first bypass, carrying the A45.
As such it is relatively long and straight. Few houses front on to it for most of its length, but there are some at its northern end.
However, the road separates a large part of Daventry from the town centre, and a lot of foot and vehicle traffic crosses it.
Mr Gibbons said: “It’s the worst road I’ve ever seen in a town. I would say one out of 10 vehicles sticks to the 30mph speed limit, some go a lot faster.
“It’s busy, there’s people crossing it, there’s junctions. It would only take a child to try and cross the road and we could have a fatal collision.
“There are traffic lights further down but that’s it really. If they put a speed camera up here they would be handing out so many fines. But I think what really needs to be done is something to slow the traffic down along the whole length.
“Zebra crossings won’t do much, I don’t think, but maybe mini-roundabouts or speed bumps.”
Northamptonshire County Council’s highways department is responsible for improvements to roads. Some work is planned along the southern part of the road to improve traffic flow as more homes are built.
A spokesman for Northamptonshire County Council said: “Investigations are still ongoing into the cause of the accident. Western Avenue, like all of our roads, is monitored by officers to look for any patterns in accidents. This information is then used to inform any decisions on what appropriate action needs to be taken.”