Rain is the number one ranking factor that stresses people while behind the wheel, with some 56% citing it in a new analysis from HiRoad. That was followed by bad weather in general (55%) and snow (52%).

However, it’s not just weather that puts drivers ill at ease. Some 50% cited other drivers using cell phones as a source of high anxiety while still others pointed to traffic (49%), potholes (47%), cyclists (45%), and speeding drivers (45%) as sources of stress.

Driving can be a stressful experience, and that in turn, has an impact on the safety of the person behind the wheel as well as fellow road users.

To find out what triggers stress in motorists, HiRoad collected 1.3 million driving-related tweets posted all around the country and used an AI tool, TensiStrength, to detect their stress levels. TensiStrength is an AI tool that detects stress levels in short pieces of text based on indicators like word choice and punctuation. 

In addition to what factors tend to stress out drivers, the analysis explores which places are most stressful for drivers.

The findings reveal that drivers in Portland, Oregon complain about driving more than in any other city in the U.S. Nearly half (47%) of the driving-related tweets found in Portland registered as stressed when they were run through the TensiStrength AI tool.

Other cities among the top five with the highest percentage of stressed tweets made by drivers include Chicago with 46%, followed by New York City, Washington, D.C., and Seattle, all with 45%.

Conversely, the least stressed drivers appear to hail from Jacksonville, Florida. Less than a third (32%) of driving-related tweets found there registered as stressed, according to the TensiStrength tool. Moreover, Tampa ranks as the second-least stressful city for drivers, with just 36% of driving-related tweets registering as stressed.

The analysis also examined the most complained about highways in the country. The findings indicate that I-90 between Illinois and Indiana is the most stressful for drivers. Nearly 46% of tweets about this highway, which passes through downtown Chicago, registered as stressed.

Other highways in the top 10 that triggered a stress reaction in drivers include a whopping six in Los Angeles alone! These include I-605 (44%), I-110 (42%), I-5 (42%), I-405 (42%), CA-57 (42%), and CA-60 (41%). Phoenix-Mesa’s I-10 and Houston’s I-69 also received ample stress tweets, both at 41%.