To meet legal and safety standards in all fifty states and Canada, the brake lights, tail lights, and turn signals of the towed vehicle must operate in sync with the motorhome. The towed vehicle will often block the warning lights on the motorhome and limit visibility. There are a wide variety of wiring solutions you can choose from to meet your individual needs.
1. You can purchase brake and signal light accessory kits that strap on or are magnetically connected to the rear of the towed vehicle. The wires from this light kit are routed to a junction box that taps into the motorhome's main wiring harness. You will need to be careful when you affix or remove the light array in order to avoid damaging the finish of the towed vehicle. A magnetic attachment system is not an option if you have a vehicle with a fiberglass body. Keep this in mind if you have more than one vehicle you plan to tow.
2. You may prefer a more permanent lighting system. With these systems, you directly connect the lights of the towed vehicle to the wiring system of the coach. The most common way to do this is to connect a wiring socket near the front of the towed vehicle and to install a wiring harness “bridge” with matching plugs at each end.
3. Another option is to permanently install an independent lighting system in the towed vehicle. You can hard-wire this system directly to the coach by installing automotive bulb sockets attached to wiring pigtails (one hot, one ground) placed inside the towed vehicle's taillight housing with a hot-lead pigtail that runs to the taillight circuits of the coach. You will need to have ample clearance inside the taillight housing to use this option.
When towing a vehicle behind your motorhome, you also may want to consider adding a supplemental braking system. In most states, if the vehicle you are towing is over a certain weight (including tow bars, dolly, or trailer), you are required by law to have a supplemental braking system. They can also make your travels much safer and easier, especially if you are driving in a lot of stop-and-go traffic or on long downhill grades. Another braking system can also help reduce the wear and tear on the motorhome brakes. Some motorhome manufacturers actually specify that supplemental braking is necessary for towing loads that exceed a certain weight. If you tow a vehicle in this situation without a supplemental braking system, you could be in danger of voiding your warranty.
While it does not affect safety, you may want to consider traveling with a cover over your towed vehicle or at least a front rock shield or bra. Your RV will throw a lot of road debris and dirt (especially if you have a diesel pusher) up behind it, and this can cause a lot of damage to the finish.