What Causes the Most Car Accidents in San Jose?
Speeding is San Jose’s top-identified primary collision factor. The City’s 2019–2023 analysis associates speeding with 24% of all crashes, followed by unsafe turn movements at 11% and red-light running at 8%.
Many competing driver accounts after a crash focus on what kind of collision happened: rear-end, intersection, sideswipe, or head-on. The common causes of car accidents in San Jose involve the driving behavior behind the collision, not just its shape.
Speeding, unsafe movements, red-light violations, distraction, and impaired driving each create different fault disputes and require different evidence.
San Jose publishes unusually detailed local crash data that identify which driving behaviors occur most often. That data gives injured people and their personal injury attorneys a stronger foundation than generic national lists. It also highlights where the evidence questions tend to concentrate when fault is disputed after a serious car collision.
Key Takeaways About Common Causes of Car Accidents in San Jose
- Speeding is the top identified cause in the City’s crash data, appearing in 24% of all crashes and 17% of those involving death or severe injury
- Unsafe turn movements and red-light running rank second and third at 11% and 8% of all crashes
- Rear-end, T-bone, and sideswipe describe how vehicles collided, not why. The driving behavior behind the crash is what drives the fault analysis
- Distracted driving is an active City enforcement concern, but current San Jose data does not place it among the top three identified crash causes
- California’s Basic Speed Law under Vehicle Code § 22350 prohibits driving faster than is reasonable for conditions, even when the speed is below the posted limit
Which Causes Appear Most Often in San Jose Crash Data?
Speeding, unsafe turn movements, and red-light running are the three leading crash causes in San Jose’s 2025 Vision Zero Action Plan, which analyzed 24,153 crashes from 2019 through 2023. These three behaviors show up at different rates depending on whether you look at all crashes or only the most serious ones.
| San Jose Primary Collision Factor, 2019–2023 | Share of Total Crashes | Share of Serious Crashes (KSI) |
| Speeding | 24% | 17% |
| Unsafe turn movements | 11% | 5% |
| Red-light running | 8% | 5% |
KSI stands for killed or severely injured. The City uses that measure to focus on crashes with the worst outcomes. These percentages come from the City’s traffic-safety data, not from court proceedings or liability findings.
Why Is Speeding Such an Important San Jose Crash Factor?
Speeding is the City’s leading identified crash cause, appearing in nearly one out of every four collisions over the five-year study period. The City calls it the top known cause of serious collisions and traffic deaths locally.
More recent data reinforces the pattern. Of San Jose’s 49 traffic fatalities in 2024, 39 occurred on streets posted at 35 mph or higher. Nine of those deaths were directly attributed to speeding. The 39-fatality concentration on higher-speed roads reflects how dangerous those streets are. The nine directly attributed deaths show that speed itself remains a leading factor.
California’s Basic Speed Law under Vehicle Code § 22350 goes beyond posted limits. It prohibits driving faster than is reasonable or prudent for weather, visibility, traffic, and roadway conditions. A driver traveling below the posted limit may still violate this law when conditions make that speed unsafe.
How Do Unsafe Turn Movements Lead to Collisions?
Unsafe turn movements account for 11% of all San Jose crashes and 5% of serious crashes in the City’s 2019–2023 data. These collisions happen when a driver turns or changes lanes before it is safe to do so.
Practical situations include turning left across an approaching vehicle’s path, changing lanes without enough clearance, or merging without signaling when other traffic is nearby. Vehicle Code § 22107 puts it plainly: a driver cannot turn or move right or left on a roadway until the movement is reasonably safe, and must signal when another vehicle may be affected.
These crashes often produce disputes about timing and who moved first. Where each vehicle was damaged, witness accounts, and available video help show which driver’s movement created the conflict.
How Often Does Red-Light Running Appear in San Jose Crash Data?
Red-light running accounts for 8% of all crashes and 5% of serious crashes during the same study period. The City’s 2025 Action Plan names it alongside speeding and unsafe turns as one of the top three violations leading to fatal and severe injuries.
Vehicle Code § 21453 requires drivers facing a steady red signal to stop and remain stopped until they are allowed to proceed. When two drivers disagree about who had the green light, the central question is which driver had the right of way at the moment of the collision.
Evidence that helps answer that question depends on the specific intersection. Traffic-signal timing records, video footage, vehicle positions after the crash, and witness observations each address a different piece of the puzzle. Not every intersection has cameras or recorded signal data.
Where Do Distracted Driving and Cell Phones Fit?
Distracted driving is an active San Jose traffic-safety concern, but the City’s 2019–2023 crash analysis does not place it among the top three identified crash causes. The City’s April 2026 Distracted Driving Awareness campaign targeted high-crash corridors and reminded drivers to put phones away and pay attention.
Vehicle Code § 23123.5 prohibits driving while holding and operating a handheld wireless phone or electronic device. The law permits limited hands-free and mounted-device use under specific conditions.
Distraction-related crashes present a particular evidence challenge. Distraction may not be apparent from the drivers’ initial accounts alone. Witness observations, phone or electronic records when they exist and are legally obtainable, and the circumstances of the crash itself may help evaluate whether distraction played a role. That evidence is not available in every case.
How Significant Is DUI in Current San Jose Traffic Fatalities?
Impaired driving appears in San Jose’s most recent fatality data at a concerning rate. The City reported that 22% of San Jose traffic fatalities in 2025 were DUI-related. During the first four months of 2026, the City reported that close to 30% of traffic fatalities were DUI-related. The June 2026 DUI safety update described that early 2026 increase as a growing concern.
Vehicle Code § 23152 prohibits driving under the influence of alcohol or drugs and sets California’s general 0.08% BAC limit for ordinary drivers. A DUI arrest does not automatically decide responsibility for the crash. The injury claim still has to connect the impaired driving to what happened and the resulting harm.
In practical terms, a DUI investigation may produce records, including alcohol or drug test results when obtained and the officer’s observations, that become relevant in the injury claim. Those records help evaluate impairment but do not by themselves answer every question about how the collision occurred.
How Do Following Distance and Lane Movements Cause Different Types of Crashes?
Following too closely, speeding, and distraction all lead to rear-end collisions, but each one raises different fault questions. “Rear-end” describes how the vehicles collided, not why the crash happened. The driving behavior behind it is what matters.
Vehicle Code § 21703 requires drivers to maintain a following distance that is reasonable and prudent for speed, traffic, and road conditions.
The difference between causes matters in practice. A following-distance dispute focuses on the gap between vehicles and the time available to react. A distraction dispute focuses on what the rear driver was doing before the impact. A speed dispute focuses on how fast the trailing vehicle was traveling relative to traffic flow. The same collision shape, but different evidence questions.
The same logic applies to sideswipe and lane-change crashes. The collision shape tells you what happened. The driving behavior, whether an unsafe lane change, failure to signal, or inattention, tells you why.
Do the Same Crash Factors Matter Across the Broader South Bay?
Speed and alcohol appear at substantial levels in Santa Clara County crash data, which provides broader South Bay context. The California Office of Traffic Safety reported 2,403 speed-related fatal-and-injury collisions and 1,030 alcohol-involved victims killed or injured across Santa Clara County in 2023.
OTS counts some figures as victims and others as collisions, so the county data does not produce a clean cause ranking comparable to San Jose’s Vision Zero analysis. The numbers do show that the same driving behaviors San Jose tracks locally, particularly speed and impairment, appear at significant levels across the broader region.
How Do Attorneys Figure Out What Actually Caused a Crash?
The cause of a specific collision is established through evidence from that crash, not citywide statistics. Citywide data shows which driving behaviors appear most often. A car crash claim examines what happened in one collision based on the available records and observations.
Different disputes call for different kinds of evidence. What matters most depends on what the drivers disagree about:
- Speed disputes draw on vehicle damage patterns, electronic or vehicle data when available, witness accounts, and road conditions
- Red-light disputes rely on traffic-signal timing records, video, witness accounts of signal color, and where the vehicles ended up
- Unsafe turn or lane-change disputes focus on where each vehicle was damaged, where the vehicles were in their lanes, and whether signals were used
- Distraction questions involve witness observations, admissions, and phone or electronic records when they exist and are legally obtainable
- DUI-related claims examine police investigation records, alcohol or drug test results when they exist, and witness observations of impairment
Each source helps confirm or contradict what a driver says happened. No single item automatically answers the fault question. The claim compares the available evidence against each driver’s version of events.
Why Does the Cause of a Crash Matter for a California Injury Claim?
The cause of a collision helps determine which driver was responsible and what evidence the claim needs. California requires the injured person to connect the other driver’s negligent conduct to the crash and the resulting injuries. Identifying the cause is the first step in building that connection.
When both drivers may have contributed, California divides responsibility between them. Under the state’s pure comparative-fault system, established by the California Supreme Court in Li v. Yellow Cab Co., recovery is reduced according to the injured person’s share of fault rather than eliminated entirely. A dispute over who ran a red light, who was speeding, or who changed lanes without clearance directly affects how that responsibility is divided.
A claim involving a serious collision in San Jose moves through fault evaluation, insurance review, medical documentation, and loss calculation. The cause of the crash is the starting point because it tells the attorneys what conduct, what safety rules, and what evidence matter most.
Frequently Asked Questions About Common Causes of Car Accidents in San Jose
What Does “Primary Collision Factor” Mean in San Jose Crash Data?
The primary collision factor is the main driving behavior or condition recorded in the City’s crash data for a specific collision. It helps the City spot traffic-safety patterns and decide where to focus resources. It does not decide legal fault in an individual crash. A separate analysis of the crash evidence is needed to determine responsibility.
Is It Possible for One Crash to Have More Than One Contributing Cause?
Yes. A collision may involve a speeding driver who was also distracted, or a red-light violation combined with an unsafe turn from another direction. The crash data records one primary factor per collision, but the actual fault investigation examines every contributing behavior and condition supported by the evidence.
Does Violating a Traffic Law Automatically Decide a Car Accident Claim?
No. A traffic violation is relevant to the fault analysis, but civil responsibility also requires proof that the violation caused the crash and resulted in actual injuries or losses. An alleged violation, whether from a citation, police report, or other source, is evidence, not a final answer. The injury claim must separately connect that conduct to what happened.
Is Phone or Vehicle Data Available to Show What a Driver Was Doing Before a Crash?
Electronic evidence may sometimes help evaluate speed, braking, device use, or vehicle activity before a collision. Whether that data exists and is legally obtainable depends on the vehicles involved, the devices present, and the circumstances of the investigation. Not every crash produces accessible electronic records.
Can M&Y Evaluate What Caused Your San Jose Crash?
When drivers disagree about what happened, reviewing the available records and evidence is the starting point for understanding who was responsible. The cause of the collision shapes what evidence matters and how the claim moves forward.
M&Y Personal Injury Lawyers offers free, no-obligation consultations for San Jose car accident claims. Call 408-521-1701 or contact us online. We handle these cases on a contingency-fee basis, so there is no attorney fee unless we win.
