@Tom_Haddon, I agree with @Heaust-ops in that the best option for lighting on a track would be light baking into a lightmap texture. This is a separate texture that you can control the intensity of directly. The reason that this is usually the preferred method for this type of scene is that the lighting will usually be static since the lights are not moving around the track and can save on a lot of calculation per frame. In addition to that, light baking usually allows for better quality lighting and shadows since they are created with ray traced renders resulting in a much higher quality in shadows and bounced light than would available in real time, especially without a powerful GPU.
This is an older thread discussing light baking, but has some good information about creating and using them. Hope this helps with your information gathering as you decide on your approach.