Dayton at the bottom of international list, which is good news for drivers

The congestion level is arrived at by computing the extra travel time required to otherwise free-flow traffic.

Drivers in Mexico City – the highest-ranked urban area – tacked on 66 percent more travel time due to congestion. China had eight cities in the top 20. Los Angeles, San Francisco and New York were the worst-congested American cities, according to the study.

Here are 5 things to know about road congestion in Dayton:

Unchanged from 2015: The 9 percent congestion level in Dayton remained unchanged from 2015 when the city was also at the bottom of the list.

Improvement over years: The relatively uncongested roadways in the area have improved further since a 12 percent rating in 2008, the first year for the TomTom index.

Worst day: The most congested day on Dayton roads last year was Jan. 20.

Time adds up: Extra 2016 travel time still added up to 10 minutes a day for Dayton commuters, or 40 hours for the year, according to the study.

Morning and evening rushes more congested: Dayton drivers navigating the morning and evening rushes, though, lost more time. Congestion for the morning peak was 11 percent and 22 percent in the evening, according to the index.

The worst evening rush congestion in the U.S. was 84 percent in Los Angeles, which also received the worst overall average ranking of American cities.

Here are how some selected cities ranked (189 total): 

1. Mexico City, 66 percent

10. Beijing, 46 percent

12. Los Angeles, 45 percent

25. London, 40 percent

35. Paris, 38 percent

49. New York, 35 percent

70. Johannesburg, 30 percent

86. Montreal, 29 percent

90. Washington, D.C., 29 percent

146. Pittsburgh, 19 percent

164. Columbus, 16 percent

169. Detroit, 16 percent

175. Cincinnati, 14 percent

183. Cleveland, 12 percent

187. Indianapolis, 11 percent

189. Dayton, 9 percent