The A483 junction with Maesbury Road on the outskirts of Oswestry reopened for drivers last week after the traffic layout was changed and traffic lights were installed.
However police, paramedics and firefighters were needed when two cars crashed just after 5pm on Monday.
Four people were involved in the crash, one of whom was taken to the Royal Shrewsbury Hospital, and there were lengthy delays while the A483 was closed for more than an hour.
A spokeswoman for West Midlands Ambulance Service said: "Two ambulances attended and treated an elderly woman for neck and chest pain.
"She was given pain relief at the scene and taken to hospital."
Two fire crews from Shrewsbury also attended to make the vehicles safe.
It comes after months of roadworks to improve the safety of the junction following a string of accidents, some fatal.
Highways England senior project manager, Jessica Kenny, said: "We know that this is a busy route for holidaymakers and local residents and I’m pleased to say that traffic is now able to use the A483 at Maesbury Road and Mile End roundabout in time for the school summer holidays."
She also thanked motorists for their patience during the work, which started in March.
"The work there will help improve traffic flows around these busy junctions, giving motorists safer and smoother journeys for many years to come," she added.
"I’d like to thank people for their patience while we carried out this important work."