A busy stretch of motorway that has been closed to traffic following a crash at 4pm yesterday could re-open this evening, the Highways Agency said.
But motorists are still being advised to avoid the affected part of the M25 on one of the year's busiest weekends for holiday travel.
The motorway was closed in Surrey after a lorry hit the central reservation yesterday afternoon, leaving three people seriously hurt.
The closure caused 28-mile tailbacks and repair teams are today working against the clock to try to fix the damage caused by the collision.
It is hoped that the hard shoulder and inside lane of the clockwise stretch between junction seven and eight will re-open this afternoon.
Work on the anti-clockwise side is taking longer because a gantry pillar must be made safe before it can be resurfaced, a Highways Agency spokesman said. It is hoped that this stretch will re-open in the early evening.
The spokesman added: "Diversion routes are working but they are very slow moving. Drivers should avoid the area if possible, or if they cannot they should allow a considerable amount of additional time for their journey."
The crash saw an HGV spill diesel on the anti-clockwise carriageway and shed its load on the clockwise carriageway. A Nissan Micra was also involved, police said.
Police, fire and ambulance crews attended the scene, and three people - the driver of the HGV and a man and a woman who were in the Micra - were taken to hospital with serious injuries.
Yesterday, tailbacks stretched 28 miles to junction 10 anti-clockwise and six miles between junctions five and six clockwise.
In the early hours of this morning there were still traffic queues stretching a mile west of junction eight.
Surrey Police is investigating the incident.