Over-Height Vehicle Causes Extensive Damage at Dartford Crossing Tunnel

An over-height vehicle caused widespread damage at the Dartford Crossing on 23 January, forcing the closure of one of Britain’s busiest river tunnels for more than 30 hours.

Experts have described the incident as “baffling” and “unfathomable,” questioning how multiple safety systems failed to stop the lorry from entering the tunnel.

The vehicle struck critical safety infrastructure along the entire 0.8-mile (1.3 km) left-hand tunnel, including overhead fans, fire suppression systems, and CCTV monitoring equipment. Northbound traffic had to be diverted to the adjacent tunnel, causing delays of up to two hours, while repair teams worked overlapping shifts to restore operations. The tunnel finally reopened at 20:00 GMT the following day.

Tunnel Layout and RestrictionsThe Dartford Crossing has two northbound tunnels, connecting Dartford in Kent to Thurrock in Essex. The right-hand tunnel is slightly larger, allowing vehicles up to 5 metres (16ft 6in) in height. The left-hand tunnel, where the incident occurred, has a maximum clearance of 4.8 metres (15ft 9in). Southbound traffic uses the Queen Elizabeth II Bridge. The A282, which carries these tunnels, is one of the busiest stretches of road in the UK, handling 150,000 vehicles daily on average and up to 180,000 on peak days.

Safety Systems in PlaceWhen manned toll booths were removed in 2015, National Highways introduced a new automated safety system to prevent unsuitable vehicles from entering the tunnels. Measures include:

• Signs: Large overhead signs warn drivers of height and width restrictions starting from junction 2 of the M25, over two miles from the crossing. Ignoring the signs is an offence.

• Sensors: Automated overhead sensors detect vehicles that are too tall, wide, or otherwise hazardous.

• Traffic Lights and Barriers: These can be activated to stop vehicles approaching the tunnel and divert them to a holding area for inspection. Vehicles deemed unsafe are either escorted through safely or rerouted.

  
  

Despite these measures, the over-height vehicle entered the tunnel, and the reason why it bypassed the safety systems is under investigation by National Highways and Kent Police. Authorities confirmed the driver allegedly failed to stop after the incident.

ReactionsLocal MPs have called for a thorough investigation and an apology to motorists and residents. Dartford MP Jim Dickson said:"I'm upset that National Highways has allowed this to happen – where you've got height restrictions, they should work."

Thurrock MP Jen Craft described the situation as “quite astounding,” noting that although procedures appeared robust, they failed on this occasion.

Experts and industry insiders have also expressed shock. Paul Hutton, a specialist in intelligent transport technology, commented that the safety measures had functioned effectively for 11 years, making this failure puzzling. Former haulage operator Rob Hollyman said it was not unusual for drivers to attempt entering the tunnels with unsuitable vehicles, but the systems normally prevent such incidents. He added:"It's unfathomable why somebody could make that mistake. We need to understand why the safety measures failed and prevent it happening again."

National Highways has confirmed that a full investigation is underway to determine how the vehicle was able to enter and cause such extensive damage.