The state of California is the most populous state in the United States, with a 2025 population of about 39.35 million people. Regular fatal auto accidents are an unfortunate reality in a state with so many people: 2023 saw 3,727 fatal accidents in California, accounting for 4,061 fatalities and involving 1,266 drunk drivers, according to data from the National Highway Traffic Safety Administration.
The five highways which saw the most fatal accidents in California from 2019 to 2023 were:
1. Interstate 5
Interstate 5 runs 1,381.29 miles from the Canadian border to the Mexican border. The I-5 in California runs 796.53 miles from the San Ysidro Port of Entry at the Mexican border to the Oregon border, just past the unincorporated community of Hilt. The I-5 runs through or past numerous cities in California, including San Diego, Los Angeles, Bakersfield, Tracy, Stockton, Sacramento and Redding.
The I-5 in California saw 536 fatal crashes from 2019 to 2023.
I-5 is considered dangerous due to:
Commercial Traffic
I-5 is a major cargo artery.
The road sees heavy, constant commercial truck traffic. This increases the risk of multi-vehicle, severe accidents.
Merging and Traffic Jams
Certain areas, such as in Sacramento and San Diego, experience fast-moving, extreme traffic merging into a reduced number of lanes, leading to collisions.
Infrastructure Problems
Many stretches of the road have poor road conditions such as limited shoulder space or lighting, debris and potholes.
Environmental Factors
Wind and fog in some areas like the Central Valley can create hazardous conditions and reduce visibility.
2. US Route 101
US Route 101 runs 1,540 miles from Los Angeles, CA to Tumwater, Washington. US 101 in California runs 808.111 miles from Los Angeles to the Oregon border, just north of Smith River. US 101 runs through or just past the California cities of Los Angeles, Santa Barbara, San Luis Obispo, Salinas, San Jose, San Francisco, Santa Rosa and Eureka.
US 101 in California saw 409 fatal crashes from 2019 to 2023.
US 101 in California is considered dangerous because of:
Merging and High-Volume Congestion
Constant, heavy traffic in places like Santa Clara and Los Angeles lead to high collision rates and severe congestion, particularly during rush hour.
Dangerous Design
Some areas, like the Gaviota Pass, have dangerous, sharp curves and narrow lanes which contribute to crashes.
Environmental Factors
Coastal rain showers and fog can significantly limit visibility.
Dangerous segments of the road include:
Ventura/Santa Barbara
This area is known for high-speed driving and dangerous curves.
Santa Clara County
This has been ranked as one of the United States’ deadliest stretches of road.
Monterey County
There are high-risk intersections to the south of Salinas.
San Mateo to San Jose
This area features a high concentration of crashes and fatalities.
3. Highway 99
Highway 99 runs 424.85 miles from the I-5 near Wheeler Ridge to SR 36 near Red Bluff. SR 99 runs through or past the California cities of Bakersfield, Visalia, Fresno, Merced, Modesto, Stockton, Sacramento and Chico.
Highway 99 saw 368 fatal accidents from 2019 to 2023.
Highway 99 has been referred to as the deadliest roadway in America.
Highway 99 is considered dangerous due to:
Outdated Infrastructure
The road was built over 100 years ago. A lot of parts of the road aren’t fully modernized to accommodate the current levels of traffic. This results in narrow lanes and short on/off ramps.
Poor Lighting and Visibility
Many parts of the highway aren’t lit at night. The Central Valley is also famous for “Tule fog” which can end up reducing visibility to 10 feet, causing pileups.
Dangerous Traffic and Merging
The road has significant agricultural and truck traffic mixing with commuters. This causes problems.
Lack of Barriers
Certain rural areas have limited protection from opposing traffic, leading to head-on collisions.
4. Interstate 15
Interstate 15 runs 1,433.52 miles from San Diego County to the Canadian border in Montana. It runs 287.26 miles in California, from San Diego County to the Nevada border near Primm, NV. The I-15 in California runs through or past San Diego, Temecula, the San Bernardino Valley, Victorville and Barstow.
The I-15 in California saw 290 fatal accidents from 2019 to 2023.
Reasons Interstate 15 in California is considered dangerous include:
The Cajon Pass
This is a 5-mile section going through Hesperia. It is plagued by unexpected high winds, dense fog and steep grades, leading to multivehicle accidents.
Speed and Heavy Congestion
I-15 is a key tourist and commuter route to Las Vegas. It experiences heavy congestion and high speeds, leading to high-speed crashes and “stop-and-go” conditions.
Commercial Trucks
I-15 is a major commercial artery. This leads to risks such as hazardous material accidents and overturned trucks.
Rising Population Density
Increased traffic volume due to Inland Empire residents has outpaced the capacity of infrastructure.
5. Interstate 10
Interstate 10 runs 2,460.34 miles from Santa Monica, CA to Jacksonville, FL. The I-10 in California runs 242.54 miles from Santa Monica to the Nevada border just past Blythe, going through or past Los Angeles, the San Bernardino Valley and the Coachella Valley along the way.
The I-10 in California saw 252 fatal accidents from 2019 to 2023.
I-10 in California is considered dangerous due to:
Extreme Congestion and Traffic Volume
I-10 is a major interstate which connects Los Angeles with Arizona and the Inland Empire. It handles massive amounts of daily traffic. This leads to stop-and-go conditions that lead to rear-end collisions.
Aggressive Driving and Speeding
Speeding is a big problem in both the desert and urban sections of the road. Drivers often travel faster than 80 miles per hour, reducing reaction time and increasing crash severity.
Commercial Trucks
I-10 is a major freight route. Large numbers of commercial trucks share lanes with smaller passenger vehicles, leading to catastrophic accidents, particularly during lane changes.
Dangerous Rural Sections
I-10 is known for single-vehicle accidents involving running off the road east of Palm Springs. These accidents are often fatal.
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