[Richard]

There are two ways to skin this cat. Both have been mentioned here. The cheapest way is to install relays at the lights. Total cost under 100 bucks. Even the newer coaches where Newell used relays for the lights suffer this issue because the wires going from the relays to the lights are too small for the amperage. There are many threads attesting to the increase in brightness just by installing the relays. All the relay really does is provide full voltage to the light.

The LED lights are relatively new to the scene. They get around
The inadequate wiring because they do not require the amperage of a traditional bulb.