Update 2.45pm: A motorcyclist in their 50s has been taken to hospital with suspected broken ribs.
Earlier: Emergency services have declared a major incident after a lorry hit a motorway bridge, causing it to collapse on one of the busiest travel days of the year.
Images on social media show the footbridge on the carriageway of the M20 between junctions three and four following the incident, and badly damaged vehicles.
Kent Police said one person had been hurt but their injuries are not thought to be life-threatening.
The M20 is the main route to the Channel Tunnel and the Port of Dover for travel to France and the rest of the Continent.
A Kent Police spokesman said: "It is believed a lorry collided with a pedestrian bridge which has collapsed on to the carriageway below.
"Officers are in attendance along with Kent Fire and Rescue Service and South East Coast Ambulance Service.
"No people are believed to be trapped in the debris, however one person is believed to have suffered injuries, not reported to be life-threatening at this time.
"Police are treating this as a major incident and the M20 has been closed in both directions to allow this incident to be dealt with. Traffic will be heavier than usual."
An estimated 13 million drivers are expected to take to the road for a holiday or an outing between Friday and Monday, according to the AA.
The busiest single day for motorists embarking on leisure journeys is expected to be Saturday, when 10 million drivers have been predicted to be getting behind the wheel.