California counties
2024 California State Highway System
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Select a shape or circle to keep that place highlighted. Counts and rates use different visual encodings.
PART 1
Explore California
Choose how to display the same transportation-safety data. Select a county or Caltrans district to inspect the underlying values.
Data: Caltrans, Crash Data on California State Highways (2024), county and district travel/crash summary tables.
SELECTED PLACE
Choose a place on the map
Values will appear here.
Exposure and crash rate
Each point represents the current geography. Horizontal position shows travel exposure; vertical position shows crash rate. Point size represents total crashes.
PART 2
Compare Places
Select up to three places. The table uses the same geography, area, road-type, and metric definitions as the explorer.
Data: Caltrans, Crash Data on California State Highways (2024), county and district travel/crash summary tables.
| Place | Road miles | Travel (MVM) | Total crashes | Injury crashes | Fatal crashes | Crash rate | Fatal + injury rate | Fatality rate |
|---|
PART 3
Vulnerable Road Users
Inspect pedestrian and bicycle fatality/injury counts on the California State Highway System. These are counts, not exposure-adjusted risk estimates.
Data: Caltrans 2024 pedestrian and bicycle fatality/injury tables by county and highway type.
| Highway type | Total | Injured | Killed |
|---|
PART 4
Statewide Freeway Trends: 2020–2024
Explore the five-year statewide freeway series provided in the Caltrans publication.
Data: Caltrans statewide five-year freeway trend table, 2020-2024.
| Year | Travel (MVM) | Total crashes | Injury crashes | Fatal crashes | Crash rate | Fatal + injury rate | Fatality rate |
|---|
PART 5
Road Risk Lab
Compare Caltrans basic average crash-rate reference groups for highways, intersections, and ramps. Values are reference rates from the published tables, not a causal simulation of a proposed road change.
Data: Caltrans basic average crash-rate tables for highways, intersections, and ramps.
Configuration A
Configuration B
DATA NOTES
What this viewer contains
This section documents scope, units, and source timing without interpreting which places are safer or more dangerous.
2024 crash and travel data
The main explorer uses the Caltrans Crash Data on California State Highways publication data supplied with this investigation. County and district values describe the State Highway System, not every local street in the county.
- Travel is shown in million vehicle miles (MVM).
- Total crash rate = total crashes ÷ MVM.
- Fatal + injury crash rate = fatal and injury crashes ÷ MVM.
- Fatality rate = people killed per 100 million vehicle miles.
Counts and rates
Count views show the number of observed events. Rate views use traffic exposure in the denominator. Both are available because they answer different questions.
Pedestrian and bicycle data
The vulnerable-road-user section reports fatality and injury counts by county and highway type. The supplied files do not provide pedestrian-miles or bicycle-miles traveled, so this viewer does not calculate pedestrian or bicycle exposure-adjusted rates.
Historical commute files
The accompanying transportation-to-work files describe earlier Census/ACS periods, largely 2000–2011. They are preserved as background source material but are not numerically merged with the 2024 crash data in this viewer.
Sources and attribution
Displayed crash, travel, trend, pedestrian, bicycle, and roadway-reference data
California Department of Transportation (Caltrans), Crash Data on California State Highways, 2024 publication tables. Caltrans Annual Collision Data
County map boundaries
U.S. Census Bureau county boundary geometry, embedded in this model and matched to the Caltrans county data using FIPS county codes.
Methodology reference
Federal Highway Administration (FHWA) network-screening guidance is used as a methodological reference for distinguishing crash frequency from exposure-based performance measures; it is not the source of the displayed California crash counts. FHWA guidance
Historical background files - not merged with 2024 outcomes
California Department of Public Health / UCSF Healthy Communities Data and Indicators Project transportation-to-work files, based on U.S. Census Bureau ACS and National Household Travel Survey data from earlier periods.