A passenger on a train replacement bus service threatened to kill the driver when he refused to pull over while travelling between railway stations.
Police are now looking for a man seen on CCTV footage from the bus camera.
The attack happened just after 17:30 GMT on 28 October between Pitsea and Chafford Hundred in Essex just after the bus had left Grays.
The man became aggressive after a request to pull over was declined and he threatened to kill the driver.
The man launched a verbal attack when the driver said the next stop would be Chafford Hundred railway station and tried to grab the steering wheel three times before managing to open the doors and leaving the bus with a woman passenger, a British Transport Police spokesman said.
"The man shown in the CCTV image may have information which could help the investigation," he added.