A cyclist was taken to hospital by air ambulance after being involved in a crash with a car and a van.
The 32-year-old female cyclist, who police said was "from London", was taken to the Royal London Hospital after the crash near Loughton in Epping New Road yesterday.
The driver of the van, a blue Citroen Berlingo, failed to stop at the scene, but was traced a few hours after the collision.
The crash, which also involved a black Mercedes E350, followed what police described as a "minor traffic incident" immediately beforehand on the Robin Hood roundabout.
Police are investigating and have arrested a 39-year-old man from Stepney, who was being questioned at Chelmsford police station this morning.
Inspector Danny Parsons said: "The Serious Collision Investigation Unit is investigating this incident. We would like to hear from anyone who may have witnessed this collision or the one earlier at the Robin Hood roundabout."
The crash happened just before 9am yesterday and the road was closed until just after 3.30pm, but police have only released details today.
Witnesses can call 101, quoting reference 310 of July 12, or email firstname.lastname@example.org.
The scene of the crash formed part of the Tour de France stage three route through Epping Forest and London on Monday.