Traffic Predict
How Many of Southern California's Freeway Traffic Sensors Still Work?
In 2010, 68% of the traffic data from Los Angeles freeway sensors came from detectors that were working. In 2026 (January to August) it was 13%. Caltrans fills in the rest with estimates. Orange County went from 82% to 52%. Right now it is worse: Orange County is down to 0%, from 54% in August.
Los AngelesOrange CountyBay Area
Right now
Share of the latest readings (1:15 pm PDT, updated every 5 minutes) that came from working detectors:
- Los Angeles and Ventura: 12% (345 of 2,809 stations)
- Orange County: 0% (0 of 1,711 stations)
- Bay Area: 59% (1,351 of 2,293 stations)
- Sacramento: 85% (1,050 of 1,233 stations)
- Inland Empire: 49% (784 of 1,601 stations)
- San Diego: 47% (387 of 830 stations)
What the numbers mean
Caltrans measures freeway traffic with detectors in the pavement: loops of wire under each lane that count cars and time how fast they pass. Their readings go to PeMS, the state's traffic database, every 5 minutes. When a detector is broken, unplugged or cut off by road work, PeMS doesn't leave a gap. It fills one in, from nearby detectors if any are working, from that detector's own past if it once worked, and otherwise from an average for a whole group of stations. Every reading is marked with how much of it was actually observed. The chart shows that share.
Filled-in numbers are fine for what PeMS was built for: statewide reports on miles driven and hours of delay, where errors average out. For a single stretch of freeway at 5 pm they can be badly wrong. One recent morning, PeMS reported the same 62.9 mph at 680 Los Angeles stations at once. Detectors that work never agree to the decimal.
This isn't new. In 2013, ABC7 reported that about a third of the 27,000 traffic sensors under Los Angeles pavement weren't working. Since then, the share of real data from the region's freeway detectors has kept falling.
How Traffic Predict handles it
- Filled-in readings that PeMS copies across many stations are left out entirely.
- On the live map, roads with no working sensor are drawn faded and marked estimated, from the working sensors on either side when they are close, or from that road's usual speed for the time (measured in the years its detector worked) when they aren't.
- Drive times on the trip pages say how much of each drive is measured right now.
- Typical speeds (the Typical view, drive-time tables and forecasts) come only from real readings, going back to the years each detector last worked.
Who can fix it
The detectors belong to Caltrans. Los Angeles and Ventura counties are Caltrans District 7; Orange County is District 12. If you want them repaired, the people to tell are Caltrans (District 7, District 12) and your state Assembly member and Senator, who set Caltrans' budget.
Year by year
| Year | Los Angeles and Ventura | Orange County | Bay Area |
|---|---|---|---|
| 2010 | 68% | 82% | 59% |
| 2011 | 64% | 79% | 52% |
| 2012 | 66% | 72% | 48% |
| 2013 | 65% | 73% | 50% |
| 2014 | 58% | 72% | 47% |
| 2015 | 59% | 74% | 48% |
| 2016 | 55% | 76% | 55% |
| 2017 | 55% | 69% | 63% |
| 2018 | 60% | 66% | 62% |
| 2019 | 58% | 76% | 65% |
| 2020 | 53% | 76% | 57% |
| 2021 | 47% | 76% | 53% |
| 2022 | 27% | 69% | 46% |
| 2023 | 29% | 58% | 57% |
| 2024 | 25% | 59% | 54% |
| 2025 | 21% | 60% | 38% |
| 2026* | 13% | 52% | 38% |
Source: Caltrans PeMS Data Clearinghouse, "Station Day" files: the average "% Observed" of mainline freeway stations, weighted by station-days. Los Angeles and Orange County use every month; the other districts January and July. *2026 so far. Updated monthly.