Here's some info about truck legal dimensions from Ontario Ministry of Transportation web site.
"HTA Weight & Dimension Limitations
An oversize/overweight permit is required when the dimensions or weight of a vehicle(s) exceeds the normal limits permitted by legislation. The following is a breakdown of the weight and dimension limitations. More information may be contained in the appropriate sections of the HTA.
Other modes of transport, such as rail, air or water, should be considered when planning a movement that exceeds the allowable limits set out in the HTA.
Maximum width:
Vehicle including load - 2.6 m
Exceptions:
1. Raw forest products (en route) - 2.8 m
2. Road service vehicles as defined in Part X of the HTA and such vehicles while they are travelling to and from a maintenance site or repair centre - no specified limit
3. Loose fodder (including rectangular and round bales of hay - no specified limit
Maximum Length:
Single vehicle including load - 12.5 m
Exceptions:
1. A fire apparatus
2. A semi-trailer
3. An articulated bus
Maximum Length:
Semi-trailer including load - 14.65 m
Definition of semi-trailer: A vehicle that is towed by another vehicle and is so designed and used that a substantial part of its weight and load rests on, or is carried by, the other vehicle or a trailer converter dolly through a fifth wheel assembly.
Note: Does not include any extension in length caused by auxiliary equipment or machinery not designed for carrying a load. "