Police are investigating after a cyclist was found lying seriously injured on the A27 Chichester by-pass eastbound this morning (Thursday, 10).
Emergency services were called to the scene near the Stockbridge Roundabout just after 7.20am.
Police said his bicycle appeared to have been struck from behind by a vehicle which did not stop.
The eastbound carriageway was closed to traffic and diversions set up.
Officers said significant delays led to motorists being advised to avoid the area this morning.
Anyone with information as to what happened is asked to report details online here, or phone 101, quoting Operation Redstone.