The StreetLight Trip Index represents trip activity but does not indicate actual number of trips or vehicles. The values are provided on an index. Personal and Commercial values use different indices. Projects in the US and Projects in Canada also use different indices.
For US Projects, the value is normalized by adjusting the number of trips in our data sample to the actual number of trips on a region around Sacramento CA, as derived from the measurements published by the California Department of Transportation. This allows us to capture monthly and seasonal variation more accurately, even as our sample grows.
For Canadian Projects, a value of 500,000 on each index corresponds to average daily traffic on a stretch of Highway 401 east of Toronto.