with one RC-box:
1. 4 lanes without additional measuring or
2. 2 lanes with split-times and/or high-speed or
3. 2 lases with refueling

with a second RC-Box resp. DIY-solution with 4 photosensors:
1. 4 lanes with 1 split-time/high-speed and refueling or
2. 2 lanes with 3 split-times each or
3. 2 lanes with 2 split-times and one high-speed-measuring for each lane or
4. 2 lanes with 1 split-time, one high-speed and one refueling

Multiple use of signals is possible, i.e. you can also use the split-time-sensor (photosensor) for refueling