Closing major thoroughfares can have a ripple effect on not only traffic flow, but also safety and fuel usage. 

A new Geotab analysis reveals London Blackwall Tunnel closures are linked to increased congestion and a threefold rise in dangerous driving.

Dangerous Driving Incidents, Miles Driven, and Travel Times Surge

Geotab's study included telematics data from more than 16,000 commercial vehicles in 2024. Key findings from the analysis include:

• Dangerous driving incidents surged by 231% on Tower Bridge during tunnel closures, with trucks — or lorries — seeing a 341% increase in harsh braking events.

• Over 5,500 commercial journeys were rerouted, resulting in an additional 91,000 miles driven on alternative central London routes in 2024.

• Average travel times increased by 43%, highlighting worsening congestion and elevated fuel consumption.

Over 5,500 journeys were rerouted on alternative roads through central London — including Tower Bridge — to avoid the Blackwall Tunnel closure, collectively covering 91,000 miles over 12 months.

"Our data shows that the Blackwall Tunnel closures have had a negative impact on traffic flow and safety in other areas,” said Aaron Jarvis, Associate Vice President of Sales and Business Development, EMEA at Geotab.

The data highlights congestion and safety concerns that won’t necessarily end when construction of the Silvertown Tunnel is complete.

The Blackwall Tunnel is undergoing closures to support the construction of the Silvertown Tunnel, aimed at reducing journey times and to help manage air pollution in south-east London. 

How New Tolls Can Impact Safety and Congestion

However, there are concerns that new toll charges for using both Blackwall and Silvertown Tunnels will increase traffic on alternative routes, intensifying congestion and safety concerns in those areas.

The average daily vehicle count on Tower Bridge increased by 18%, which caused a a surge in dangerous driving incidents due to higher congestion levels. This could also impact pedestrian safety for people walking on the bridge.

“We cannot say now whether the introduction of a toll to the Blackwall Tunnel for the first time since it opened in 1890 will continue the displacement of road traffic to these other areas, but we do know that commercial vehicles spending more time on the road going shorter distances is not good for local communities, the economy, air pollution, or driver well-being," Jarvis added.

Geotab’s recent mental health survey highlighted the impact of driver stress with 90% of lorry and van drivers saying work-related stress negatively impacts their driving. 

For many, congestion heightens concerns about job performance, safety, and overall well-being.

“These disruptions add significant challenges for commercial drivers who are under constant pressure to meet delivery schedules," Jarvis explained. "The additional time spent in congestion not only increases operational costs but also contributes to increased driver stress, as they navigate unpredictable travel conditions." 

Commercial fleet managers are forced to adjust driver schedules to accommodate for greater traffic volumes.