Originally Posted by
Lee Schierer
There are hydraulic surge brakes which are activated by the trailer pushing against the hitch when the tow vehicle slows down quickly.
Inertial/surge brakes are standard on UHaul trailers that have brakes as well as many boat trailers and Euro horse trailers, for example. (Required in Europe because they don't depend upon a connection to the tow vehicle that can fail, etc.) They can be pretty practical for utility trailers, etc., as they work well within their design. For heavy towing, electric brakes are a little more versatile because behavior can be changed on the fly to suit changing or unusual situations.
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