The A41 had to be closed this morning after a two-car smash close to the Bourne End southbound exit sliproad.
Police were called just before 7.30am and paramedics also rushed to the scene.
A man aged in his 30s was taken to hospital.
The road, which was closed from the Berkhamsted junction, was reopened by police just after 9.15am.
The vehicles involved were agrey Skoda Fabia and a red Renault Megane.