Basic question: how wide is a "lane" on a racetrack?

[Travis Stone]

The position of the gate varies from track to track. Some set it x feet from the rail, others set it y feet from the rail. I did a project once and found a starting gate company's website and used their dimensions for the width of a stall as the "lane width." However, it's not a Track and Field situation and horses can occupy more than one lane.

I believe the stall width was ~36 inches.