WAIT..I forgot. Each provence is different.Some allow for more. But you have to have permits to run from one into the other over length.
Like in the USA..which is 65 foot max, some states allow for more weigh. Like Michigan which allows for 165 thousand pounds gross if you have the right axle configuration. That is within Michigan only. Then there is a reciprocation into WI (12 Miles) if you have the proper permit.
Can’t speak to overall length, but the largest trailer is 53’ in PRC (Politically Repressive Canada). I would believe that max length would be fairly standard across N. America.