Hope he's OK.
Slow response of ambulance may well be an issue. When I witnessed a motorbike crash a few weeks ago, I called the ambulance but it took 20 minutes to arrive, despite being only a few minutes drive from the nearest ambulance station (so I was told). But quickly getting a paramedic, or at the very least a trained first-aider, to the scene is best. Those first few minutes at the roadside can be absolutely crucial.