Police have released a CCTV image after an accident involving a motorcyclist and a pedestrian on the M1 left a man with serious arm and shoulder injuries.
Hertfordshire Constabulary said the incident happened at junction six on the southbound carriageway at 3.45pm.
Officers said that a man got out of his vehicle and was involved in a collision with a motorcycle, which then failed to stop.
PC James Wood, who is investigating the incident said: "We are very keen to speak with the driver of this motorcycle as we believe they may have vital information which could assist our investigation into this collision.
"Is this you, or do you know who it may be?
If so, please call Pc James Wood or PC Leon Bennett on 101 quoting ISR 457 of October 15th.
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