I’ve got a basic road line set up with about 10 vehicles servicing.  A better vehicle has been released, so I bought a couple of those.  But they can’t get past the slow cars that I already have out there.  Is the only option to eliminate all of the slow cars so that the new ones can go at full speed?  Is there an efficient way to do this?  I hate sending cars to the depots, because I lose the passenger revenue, but if that’s the only way to do it.  Is there a way to “replace this old vehicle with this newer one”, aside from the separate steps of sending the old one back and creating a new one?

Thanks.

Regarding your second question, in the window of whatever line, there is a tab that offers you the possibility of automatic vehicle replacement.  You can set the vehicle that will replace the old one and at what time (how old has the vehicle to be in order to be replaced), but note that there are several shortcomings:

1. The new vehicle will be automatically replaced when the old one reaches the following stop, but unfortunately all cargo/passengers will be lost.  And those lost cargo/passengers will negatively count for the line/industry statistics.
2. If the vehicle you have set for replacement or any part of it becomes obsolete with the pass of time, automatic replacement won’t take place any longer and you won’t be notified.