OK. If the vehicle can run on AC or DC, there is at least a diode or rectifier in the car converting to DC for the motor. Depending on whether there are other components this could drop the supply voltage in the car. That would explain the circuit working externally but not in the car's circuit.
If you are using a flasher LED, it will flash all other LEDs in series with it, no matter where it is in the series circuit. It will need to be in its own circuit with a current limiting resistor.
Without knowing what circuit components are in the car, one option is to create 3 circuits as I described in my first post and run them off track power (center roller and frame/ground). This will bypass the circuit in the car. Use the LED calculator to get the value of the current limiting resistor for each circuit. Enter the maximum DC voltage that will be applied to the track. This assumes that there will be no reversing switch that changes the polarity. The downside is that they may not light at lower voltages.
Constant lighting will require a voltage regulator. Electronics Gurus Gunrunner John and Stan may weigh in on this. Also Lee Willis is the expert on all things 'Streets. I suggest doing a forum search on his posts.
Bob
