Comment Yes this is the biggest reason. (Score 1) 187
Whoever is at fault large scale transportation projects are one if the two main drivers for all short term changes in traffic patterns. The other is weather.
The tail end of the economic bubble and the first round of stimulus programme projects led to high levels of construction. Those projects likely completed between 2010 and 2012. As they completed road capacity increased faster than demand or traffic load. Hence reduced congestion over that time.
Last year it is possible more projects started up causing lane and road closures again. Also as I mentioned weather can be an issue. The flooding in Alberta Canada and in Colorado for example caused extended closure of damaged roads. Also the very cold winter discourages use of public transportation in most cities as nobody wants to walk to a stop and wait for a bus or train outdoors in freezing weather...plus public transportation can be very unreliable in bad weather....more so than using personal vehicles. This may br a long term thing too. The climate is changing (NOT warming... where I live average temperature has gone DOWN most of the last 10 years and it is noticeably colder than at the turn of this century especially...all year but especially in winter...this rapid cooling has changed snowpack melting and caused flooding issues more typical of what happened 100 years ago). Whether you live where it is warming or where it is cooling she effects of weather on traffic are likely to become more pronounced.