one-wheel trailers (tandem trailers) with integrated seat, handle bars, and drive train, that normally attaches to the bike via the seat post (and operate very much like a tandem). These allow small children who can't yet ride a bicycle alone to accompany adult riders as participants and motive-power producers. These trailers are by far the most popular style. Canoe and kayak: designed for towing long, thin, relatively light-weight loads such as canoes, kayaks, or wind surfing rigs. Disabled passenger: made for safely towing wheelchairs with persons in them. Pets: for carrying small domestic animals, especially dogs, that weigh less than 100 lb (45 kg). Electric trailers Electric bike trailers are trailer with electric propulsion. Most are electric pusher trailers. They are made by various manufacturers. Examples are Aevon Trailers (Cycloboost), Ridekick International (Ridekick), Topeak (Journey Trailer), etc. Limits on load Heavier loads on trailers increase the safety risks. Trailers with brakes (often referred to as braking trailers) allow heavier loads to be safely towed. According to the ASTM standard, a limit of can be carried in a trailer without brakes. On the other hand, the European standard for the maximum load is . The heavier the load, the more hazardous the ride becomes due to the inability to stop the trailer from continuing to move forward into the cyclist. This hazard can be diminished if a braking system is added to the trailer, typically some form of overrun or inertial braking system. Components Axle Most trailers have a separate axle for each wheel, like those used on a bicycle. These separate axles usually mount directly on the frame using either threaded nuts, a quick-release mechanism, or some press fit arrangement. The use of separate axles for two-wheel trailers allows the load carrying area to be between the wheels with its base below the axles, so as to keep the centre of gravity relatively low. Some trailers support a normal axle on two sides, others mount the wheel off one side with a stub axle (a one sided axle). Brakes Drum Brakes: Currently the only type of brake that may be found on bicycle trailers are drum brakes with an inertial rotating actuator. Fender/mud guard If included, the fender (or just a mud flap) helps to protect the cargo and the towing bicycle from road spray and dirt. On heavy-duty trailers, the fender may be designed to be capable of bearing