LongBeach TripUpdates¶
Jan 2026 Summary¶
Generally, we want better transit user experience. Specifically, the performance metrics we can derive from GTFS RT Trip Updates distills into the following objectives:
Increase prediction reliability and accuracy
Increase the availability and completeness of GTFS RT
Decrease the inconsistency and fluctuations of predictions
Schedule + RT Summary Stats¶
General RT Metrics¶
Update Availability Goal 1: 2+ vehicle positions or trip updates messages per minute.
Update Availability Goal 2: 100% routes are covered by RT, and 75%+ of trips have RT.
Prediction Accuracy Metrics¶
Update Availability Goal: 90%+ of minutes has predicted arrival information.
Bus Catch Likelihood Goal: 75%+ of predictions result in catching the bus.
Prediction Error Goal: Closer to zero or smaller positive values (early predictions). Late predictions = negative values = riders miss bus
Prediction Error Percentiles¶
Distribution of Prediction Errors¶
The 50th percentile is the typical or median rider experience, and it can show that, on average, this transit agency is roughly on-time.
If the 10th percentile is fairly close to the 50th percentile, it means that the transit agency is consistent and reliable in its predictions.
Extreme values for the 10th percentile would indicate that predictions fluctuate, or, are somewhat unreliable.
Steeper lines indicate fairly reliable predictions for the rider.
Accuracy Loss¶
Ratio of the 10th to 50th percentiles
Newmark’s paper on a small sample of transit agencies suggests that the positive prediction errors typically have ratios of 4.
Late predictions (negative prediction errors) have ratios around 3.
Steeper lines = less accuracy loss = better
y-axis is percentile (moving from 10th to 50th percentile is moving from upwards on y-axis)
x-axis is error (smaller change along x-axis is less accuracy loss).
less accuracy loss = less change along x-axis, since change along y-axis is constant (10 to 50) = steeper (unintuitive to the normal interpretation of slope!)
Route Map by Priority Criteria¶
The following layers are available and selectable (if no routes match the criteria, the layer is excluded):
Average prediction error (minutes) for all routes
Routes with <90% update completeness Providing complete real-time information for all routes is the crucial foundation.
Highly Variable Routes (IQR > 3) that could benefit from transit-supportive policies (signal priority, bus lanes). The variability in prediction accuracy here could be due to the local traffic conditions.
Routes with Bus Catch Likelihood (early + on-time accuracy < 75%), or late predictions 25% of the time.
Route Summary¶
Prediction accuracy varies by routes. The routes shown at the top have high variability (high IQRs).
High variability = high IQRs: local traffic conditions mat confound the prediction algorithm. For these routes, a focus on improving service reliability through additional infrastructure (signal priority, bus lanes), or other transit planning and policies could be explored.
Negative 25th percentiles: riders miss the bus (late predictions). These routes may benefit from service reliability improvements for riders.
Interpretation: A value of -5 means that one quarter of riders miss the bus by 5 minutes.
scaled IQR: IQR adjusted so predictions closer to the bus arrival are weighted more. Predictions 5 minutes out are more important than predictions 25 minutes out.