Eyewitness Rahul Tandon, who lives in Halifax, told BBC Radio Leeds he was driving the first car to be stopped by police on the slip road at junction 24 of the M62 as the drama unfolded.
"As we pulled off the motorway we could see a lot of police vehicles, a lot of flashing lights," he said.
"We were basically the first car that was stopped by police and we just waited and waited. Over the next 10 or 15 minutes there was frenetic activity as more and more police vehicles arrived.
"At about 6.15 to 6.20 policemen were running up the slope to the ambulance and beckoning them to come quickly."
He said the police eventually told him and other drivers to reverse back up the slip road and on to the M62 to leave the scene.