Drivers in the UK are stuck in traffic for up to 12 days a year, according to new figures - with Belfast named the third most congested British city.
Inrix, a traffic information company, used real-time data over four years in a study for the Sunday Times. It established average speeds and congestion levels in 18 urban areas to calculate the hours lost in congestion.
London drivers in 2015 were the worst affected and found to be stuck in jams for an average of 101 hours a year - up from 72 hours in 2012 - a 40% increase.
Greater Manchester was second with 51 hours lost to drivers in 2015, up from 45 in 2012.
And Belfast drivers were found to have spent 38 hours in traffic delays in 2015, compared to 31 in 2012 - a 22% increase.
The deterioration has been blamed on factors like segregated cycle lanes and poorly-planned roadworks.
The latest figures are substantially lower than a separate survey in March this year by the TomTom Index, which named Belfast as the worst UK city for traffic congestion and the 14th worst in the world.
The TomTom Index said drivers in Belfast in 2015 were wasting 195 hours in traffic jams, more than eight days. This was more than twice the 2014 figure of 94 days.
The difference in the results comes down to different recording methods - TomTom compares journeys at peak and quiet periods, the time drivers could have saved without traffic jams.
Inrix record the actual time spent in traffic jams.
Roads expert, Wesley Johnston, said both results showed the Belfast traffic system was still under-performing. "For these surveys, it all depends how they're measuring it," he said.
"Historically, the problem in Belfast is that we're a very car-dependent city. One reason for that goes back to the Troubles - in the 1970s, there was a flight away from public transport because of the conflict," he said.
"There was a reticence to use buses and, in some parts of the city, buses stopped running entirely. We saw an increase in suburbs, compared to other cities because people wanted to get out of Belfast.
"In the 1980s, places like Bangor, Newtownards and Newtownabbey grew exponentially. We tend to be more likely to live outside the town centres and be more car dependent."
Mr Johnston suggested there were three priorities for improving Belfast's roads: overhauling the busiest bottlenecks; switching to public transport; and making cyclists feel safe.
"In Belfast, the York Street exchange is definitely the number one priority because it's the meeting point of the three busiest roads in the province and, also, crucially, it's the main access point to Belfast port," he said.
"The traffic means people are tempted to use Dublin port instead, which loses income to Northern Ireland."
However, in September Infrastructure Minister Chris Hazzard said Brexit had thrown the £165m York Street project into doubt, as a substantial portion of the funding - believed to be around 40% - was to come from the EU.
On public transport, Mr Johnston said: " The city can't absorb the number of cars going into it in the morning. There isn't really any way to fix that unless you switch to other modes of transport, or tarmac over most of the city centre. Park and Rides in places like Cairnshill and Dundonald are steadily growing in popularity. It's a great idea for people who live in rural areas."