Oxford has seen the biggest increase in traffic congestion of anywhere in UK, according to new figures released by TomTom.
The city has risen from sixth to third place in a nationwide congestion ranking which shows nearly a third (31.2%) of its main roads are clogged with traffic.
Traffic expert TomTom has measured the top 50 most congested areas across Britain in the past six months. Findings suggest that while congestion is worst in London and Edinburgh, it has increased most in Oxford - by 2.2% since March.
Belfast has seen the second biggest increase in congestion, followed by Bolton, Southampton and Sheffield.
In Scotland, Edinburgh, Glasgow and Aberdeen are all in the top 10 cities that have seen the biggest increase in traffic jams in the past six months.
Road congestion is estimated to cost the UK economy £20 billion a year in lost production. It is also estimated that a reduction of just 5% in travel time for all business travel on the roads could generate around £2.5 billion of cost savings, by reducing missed appointments and speeding up delivery times.
The new research marks the launch of the TomTom International Traffic Foundation. The not-for-profit Foundation will bring together key stakeholders from academia, industry and policy-making to collaborate to reduce traffic congestion.
It will nurture talent in the field of traffic management, funding PhD and post-doctorate research, publishing research papers and hosting a number of traffic-related events.
The study shows that, perhaps unsurprisingly, London is the most traffic clogged city in the country, with 36% of roads significantly more congested during rush-hours than at off-peak times.
At number two is Edinburgh with a congestion rate of 33%.
Behind Oxford in fourth place is Belfast where 31% of roads are classed as congested, followed by Bradford (30%) and Manchester (30%), and Birmingham (28%).
The least congested big towns or cities are Northampton, Warwick and Chesterfield, all with congestion rates of less than 10%. Only five in the top 50 have seen congestion fall over the past six months: Bedford, Colchester, Newport, York and Chester.
TomTom's research is based on its real travel time database, which has collected more than four trillion speed measurements to date with over a billion new measurements recorded each day.