Navigation company Tomtom has been allowing owners of its GPS units to opt into sharing their driving data since 2011 and published its first congestion index in the first quarter of 2012. It just released its survey for all of 2012 and found that Los Angeles had the worst traffic congestion in the US last year. 

Tomtom uses the data that comes from drivers to find out how much time it takes to drive in cities given optimal situations and in traffic at various times of the day. It uses the data to find how much time as a percentage is added to a journey during congested periods.

For Los Angeles, Tomtom found that the average congestion adds 33% to the average journey. So for a journey that could take an hour in optimal conditions, the average traffic congestion adds 33 minutes to the journey. At peak times, it adds 39 minutes for each hour driven. That means that drivers will spend more time sitting in traffic in an hour at peak congestion than actually driving. For drivers with a 30-minute commute, they will waste 90 hours in traffic. 

Average congestion in North America ticked up slightly to 18%, which is about 1% worse than at the beginning of the year. 

If you want to see where your city ranks whether you live in North America, Europe, Australia or Africa, you can view Tomtom's index here. 

1. Los Angeles, California

Los Angeles ranks as the most congested city in North America. The study found that congestion adds 33% to journeys, but at the evening peak, it adds an amazing 77% a drive. At peak periods, it will add 39 minutes for every hour driven that calculates to 90 hours per year for each half hour of commute time

2. Vancouver, British Columbia

Vancouver traffic is nearly as bad as Los Angeles. Average congestion is 32% with an evening peak of 68%. At peak traffic, it adds a delay of 35 minutes for each hour driven and adds 84 hours a year for each half hour of commute.

3. Honolulu, Hawaii

At least if you are sitting in traffic in Honolulu, there is a gorgeous view. Average congestion is 30% with an evening peak of 68%. During peak traffic there is an average addition of 36 minutes for each hour driven, which adds 86 hours for each half hour of commute over the course of a year.

4. San Francisco, California

San Francisco is another traffic nightmare in the US. Average congestion adds 29% to a journey and the evening peak adds 69% to a journey. The traffic adds 35 minutes for each hour driven and 84 hours a year for each half hour of commute.

5. Seattle, Washington

Seattle is yet another West Coast city with bad traffic. Average congestion adds 21% to a journey. However, the evening peak increases time of a journey by 73%, which was the second highest that the study found. It adds 35 minutes for each hour driven at peak congestion or 84 hours a year

6. Toronto, Ontario

Toronto is the first East Coast city on the list. Congestion adds 25% to the average journey and peaks at 62% at the evening peak. At peak periods it adds 33 minutes per hour to a journey and adds 81 hours a year compared to an uncongested commute.

7. San Jose, California

It is back to the West Coast for the seventh spot. San Jose is known for its beaches, but congestion adds 25% to the average journey and hits 69% at the evening peak. There is an average 35 minutes of added time for each hour at peak times, and it adds 84 hours of driving each year.

8. Washington D.C

Washington D.C is famous for its bad traffic, and it is the second worst on the East Coast according to Tomtom. Average congestion adds 25% to commutes and adds 59% to commutes during peak times. It adds 31 minutes for each hour of driving during peak periods and adds 78 hours a year. 

9. New Orleans, Louisiana

New Orleans is the sole Southern city in the top ten. Average congestion adds 25% to drives and adds 57% at peak times. It adds 29 minutes to each hour driven at peak times and adds 74 hours of driving per year. 

10. Montreal, Quebec

The final city in the top ten is also the third city on the list from Canada. Montreal traffic adds 25% to the average commute and adds 71% during peak times, the third highest. Outside of peak times, Montreal traffic was much better than other cities in the top ten. The traffic adds 36 minutes for each hour driven and 86 hours a year

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