What the colours mean
Congestion is relative to each road's own
free-flow speed — not an absolute speed.
Free flow — under 15% slower
Moving at or near this road's normal speed
Moderate — 15–30% slower
Noticeably slower than normal
Heavy — 30–60% slower
Substantial delay
Severe — over 60% slower
Trip takes more than 1.6× the free-flow time
ClosedRoad reported closed
No dataNo reading for this interval
This is why green on a highway is much faster than green on a side
street. A highway at 62 mph against a 65 mph free-flow is 5% slower →
green. A side street at 23 mph against a 25 mph free-flow is 8% slower →
also green. Both are "normal for that road."
Formula: congestion % = (duration − baseDuration) ÷ baseDuration.
baseDuration is HERE's free-flow reference for that road — the
unimpeded travel time. typicalDuration is what's normal for this
time of week. Hover any segment for its speed, free-flow speed and delay.