| Speed of veschile | v | m/s |
| Separation distance | d | m |
| Length of veschile | l | m |
| Flow | f | veschile/sec |
How long does it take the second veschile to replace the first?
t=(l+d)/v
How many veschiles pass in a minute? f=60*v/(l+d). This is a flow.
Problem is to maximise f.