How we estimate street speeds
We estimate speed between stops from bus locations. Recent passes count more: their weight halves every 10 minutes. When recent passes are sparse, we also use the usual speed for that day and hour, where available.
If no bus has passed in 90 minutes, we use that hour’s history, then the average across all recorded days. In Typical week, missing hourly history also falls back to that average. Street details identify the source. Brighter lines use recent passes; faded lines use historical estimates. Gray means no speed history.
The citywide color scale is centered on the median across recorded street sections. Its ends are the slowest and fastest 5%. The comparison scale uses each section’s usual speed for the selected hour, falling back to its average across all days.
Bus trails show the last 5 minutes. Hollow bus markers mean the CTA reports a delay; a ring means the bus has stayed in place for at least 2 minutes mid-route. A dashed link marks buses running close together.