London has been crowned the world's slowest capital city for driving, with motorists losing an average of 148 hours, nearly six full days, to traffic congestion during 2025 according to data released by navigation technology company TomTom in January 2026. The dubious distinction reflects worsening gridlock driven by public transport strikes forcing commuters into cars, expanded 20mph speed limit zones championed by Mayor Sadiq Khan, and road space reallocation prioritising cyclists and buses over private vehicles.
TomTom's annual Traffic Index, which analyses congestion levels in over 600 cities globally using anonymized data from millions of connected devices, found that journeys covering just one kilometre, approximately 0.6 miles, in central London took an average of three minutes and 40 seconds during 2025. This represents a 2 percent increase from 2024's already glacial pace and translates to an effective average speed of roughly 16.4 kilometres per hour, or just over 10 miles per hour across the congestion zone.
The 148 hours annual delay figure assumes a driver commuting through congested areas during peak periods throughout the year. For context, this represents nearly 19 full working days lost to sitting in traffic, or approximately four percent of waking hours for someone working full-time. The financial cost, calculated based on fuel consumption, vehicle depreciation, and lost productivity, amounts to approximately £1,840 per driver annually according to transport economics researchers at Imperial College London.
Tube Strikes Force Drivers Onto Roads
London Underground strikes proved a significant factor worsening 2025 congestion. Multiple walkouts by RMT union members over pay disputes and working conditions shut down substantial portions of the Tube network for 28 days throughout the year, forcing hundreds of thousands of regular public transport users to seek alternatives including driving, buses, cycling, or working from home.
During strike days, traffic volumes increased by an average of 23 percent compared to typical weekdays according to Transport for London monitoring data. Central London roads, already operating near capacity under normal conditions, became completely gridlocked as drivers who would ordinarily take the Underground added to baseline traffic volumes.
The strikes created particular chaos during morning and evening rush hours when Underground trains typically carry their heaviest loads. With that capacity unavailable, commuters either drove themselves, increasing private car volumes, or shifted to buses, which then became overcrowded and delayed by increased traffic, creating cascading failures across the entire transport network.
"The Tube strikes had a devastating impact on London's traffic flow," explained transport analyst Rachel Aldred of the University of Westminster. "The Underground carries over four million journeys daily. When even a fraction of those passengers shift to cars, the road network simply cannot absorb that volume. We saw 40 to 50 percent increases in journey times on strike days, with residual effects lasting into following days as the backlog cleared."
20mph Limits Slow Traffic Flow
Mayor Sadiq Khan's expansion of 20mph speed limit zones throughout London boroughs contributed to slower average speeds and increased journey times, though the policy's congestion impact proves more complex and politically contentious than headline figures suggest.
Transport for London expanded 20mph limits across approximately 220 additional kilometres of roads during 2024 and 2025, bringing the total network covered by reduced limits to over 560 kilometres. The stated rationale emphasized road safety, with data showing that pedestrian fatality risk drops substantially when struck by vehicles at 20mph versus 30mph.
However, critics including motoring organizations and Conservative politicians argue that blanket 20mph limits on roads where conditions don't warrant them create unnecessary congestion by forcing traffic to travel below speeds that road design and conditions would safely support. On wide, straight roads with good visibility and minimal pedestrian activity, artificially limiting speeds to 20mph creates bunching and stop-start traffic patterns that reduce overall network capacity.
Research by traffic engineers suggests that 20mph limits' congestion effects depend heavily on implementation context. On narrow residential streets with high pedestrian activity, 20mph limits improve safety with minimal journey time impact because average speeds seldom exceeded 25mph previously. However, on major through-routes where traffic previously flowed at 30mph, reducing limits to 20mph can increase journey times by 30 to 40 percent while providing questionable safety benefits on roads with limited pedestrian crossings.
Khan defended the policy during a January 2026 interview with LBC radio. "We cannot sacrifice Londoners' safety to save motorists a few minutes. The evidence clearly shows that 20mph limits save lives and reduce serious injuries. Yes, this means some journeys take slightly longer, but that's a trade-off we must accept for safer streets."
Road Space Reallocation Compounds Delays
London's ongoing transformation of road space from general traffic lanes to cycle lanes, bus lanes, and pedestrianized areas further constrains vehicle capacity, contributing to worsening congestion even as overall traffic volumes remain relatively stable or decline slightly.
Transport for London data shows that total vehicle kilometres driven in central London decreased by approximately 3 percent between 2019 and 2025, yet journey times increased substantially over the same period. This apparent paradox stems from reduced road capacity due to lane conversions and restrictions meaning fewer vehicles can travel more slowly on the remaining available road space.
Major schemes including the expansion of cycle superhighways, creation of low-traffic neighborhoods restricting through-traffic on residential streets, and pedestrianization of areas including Oxford Street and sections of the South Bank concentrated remaining traffic onto fewer arterial routes. These routes, already heavily used, became bottlenecks that constrained entire network performance.
Supporters argue that road space reallocation delivers benefits beyond simple journey time calculations. Increased cycling and walking improve public health, reduce air pollution, and make streets more pleasant for residents. Bus lanes carrying dozens of passengers per vehicle should receive priority over private cars carrying one or two people. The congestion experienced by remaining drivers represents unfortunate but necessary consequence of rebalancing London's transportation system away from car dominance.
Critics contend that ideology rather than evidence drives policy, with anti-car sentiment motivating schemes that worsen congestion, damage businesses dependent on deliveries and customer access, and disproportionately burden working-class Londoners including tradespeople and shift workers who cannot easily use public transport or cycling for their journeys.
International Comparisons Reveal London's Outlier Status
TomTom's data ranking London as the world's slowest capital city places it behind cities including Dublin, Edinburgh, and Paris that also suffer significant congestion but maintain slightly better traffic flow than Britain's capital. Dublin drivers lost an average of 143 hours to congestion in 2025, while Edinburgh recorded 141 hours and Paris 139 hours.
However, London's congestion proves particularly severe compared to global cities of similar size and economic importance. New York drivers lost 117 hours annually, Tokyo 89 hours, and Singapore just 78 hours despite all three being major global financial centres with dense populations and substantial traffic volumes.
The comparison highlights that congestion stems not inevitably from city size or economic activity but from policy choices about transportation infrastructure investment, road capacity management, and modal split between private vehicles, public transport, walking, and cycling.
Singapore's relatively modest congestion reflects decades of aggressive vehicle ownership restriction through certificate systems making car ownership prohibitively expensive, combined with world-class public transport and road pricing that charges drivers for using congested areas during peak times. Tokyo benefits from comprehensive rail networks that capture vast majority of commuter trips, leaving roads primarily for deliveries and essential vehicle trips.
London's congestion thus reflects policy failures spanning decades. Underinvestment in public transport capacity, particularly rail connections to outer London suburbs, forces car dependency for many journeys. Road pricing through the congestion charge, introduced in 2003, helped initially but has not expanded or increased charges sufficiently to manage demand as city population grew. Failure to deliver promised Crossrail 2 and other major transport projects means the network cannot absorb continued growth.
The Economic and Social Costs
Beyond individual driver frustration, London's congestion imposes substantial economic costs that ripple through the entire regional economy. Freight and delivery vehicles stuck in traffic increase costs for businesses, which pass those expenses to consumers through higher prices. Tradesperson time lost to congestion reduces productivity and forces higher charges for services. Emergency vehicle response times suffer when fire engines, ambulances, and police cannot navigate gridlocked streets quickly.
Air quality deteriorates as vehicles idle in traffic, with particulate matter and nitrogen dioxide emissions concentrated in areas where congestion proves worst. The health impacts fall disproportionately on residents of high-traffic areas, often lower-income communities living along major roads.
The psychological and quality-of-life impacts prove harder to quantify but equally real. Spending six days per year sitting in traffic creates stress, reduces time available for family and leisure, and contributes to the perception that London has become unliveable for anyone dependent on road transport for their daily activities.
Some researchers argue that congestion ultimately proves self-limiting through induced demand theory operating in reverse. As driving becomes sufficiently unpleasant, people shift to alternatives including public transport, working from home, or relocating closer to employment. This behavioral change reduces traffic volumes over time, albeit through forcing people to adjust their lives around transportation dysfunction rather than solving underlying problems.
Political Fallout and Future Prospects
Mayor Khan faces sustained criticism from political opponents who blame his policies for worsening congestion. Conservative candidates in the 2024 mayoral election campaigned heavily on reversing 20mph limits, removing cycle lanes, and scrapping the expanded Ultra Low Emission Zone, though Khan won re-election suggesting Londoners accepted his transportation vision despite congestion concerns.
The Labour government elected in 2024 generally supports Khan's approach, making major policy reversals unlikely even as congestion worsens. Transport for London's financial position, strained by pandemic revenue losses and government funding constraints, limits capacity for major new infrastructure investment that might alleviate congestion through expanded public transport capacity.
Technological optimists suggest that autonomous vehicles, ride-sharing, and mobility-as-a-service platforms could eventually reduce congestion by improving vehicle utilization and enabling more efficient routing. However, these technologies remain years or decades from deployment at scales that would meaningfully impact London's congestion.
More immediately, continued expansion of remote and hybrid working following the pandemic reduced peak-hour commuting somewhat, though this trend appears to have plateaued as employers demand greater office presence. The long-term impact likely involves some permanent reduction in peak traffic versus pre-pandemic levels, though not sufficient to solve congestion absent other interventions.
London's status as the world's slowest capital city for driving reflects decades of accumulated policy choices, infrastructure underinvestment, and competing visions for urban transportation. Whether current trends continue worsening, stabilize at current levels, or eventually improve through behavioral adaptation and policy changes remains uncertain. What seems clear is that for 2025's London drivers, the experience involved spending nearly six days stuck in traffic watching their city creep past at 10 miles per hour, a pace that horse-drawn carriages would have recognized 150 years ago when London last moved this slowly. Progress, apparently, sometimes moves backwards.