We know that we need to arrive at an internal tunnel luminance Lin, and we know we start at the formula for calculating the curve is the one given above, Ltr.
Time and distance are related by the fixed velocity, v, of the tunnel project. If we get the time taken to go through the transition zone we can easily get the length of the transition zone.
Re-arranging the original equation...
So you can calculate d, the length of the transition zone, from these three things:
- the project velocity
- the threshold luminance
- the internal luminance.