How long does an underpass have to be to have a ventilation system?

[roadman65]

Just curious to know how long an underpass has to be to have a ventilation system?  In New York on I-95 under the Westchester Avenue and White Plains Road Circle, there are ventilation fans in the ceiling to ventilate the long underpass.  Then in Washington, DC, the 12th Street Tunnel is also equipped with a fan that can be seen on the ground on the Washington Mall that the tunnel passes under.

Yet the Colonial Parkway tunnel under Colonial Williamsburg has no ventilation system at all!  I am guessing cause its not long enough and has light traffic on it, for it to be exempt from being ventilated either by fans or ventilation buildings nearby.

What are the rules for tunnels and ventilation?

[cbeach40]

I can't speak to other jurisdictions, but for Ontario ventilation is required at 240 m.

[oscar]

Then in Washington, DC, the 12th Street Tunnel is also equipped with a fan that can be seen on the ground on the Washington Mall that the tunnel passes under.

The part of D.C.'s Third Street Tunnel carrying I-395 under the National Mall has ventilation shafts at both ends. AIUI, the headquarters buildings for the Labor Dept., and for Health and Human Services, were built about the same time as the tunnel, and were built around the ventilation shafts.