A good guess is that there is as much as 400 million tonne of freight moved by all trucks over the highway in Canada every year. Trucks today, however, are far more fuel efficient than trucks ten or twenty years ago. In 1975, a typical load of a little over 20 tonne could be handled for about 36.1 litres of fuel per thousand tonne-kilometre. And this only is considering 'typical' loads. There are a lot of big trucks that do considerably better than this.
Trucks handle over half of all of Canada's trade as measured by the value of the commodities.
No wonder there are close to ten million truck trips a year back and forth across the border. The complete profile is available from the Canadian Trucking Association or any one of the provincial trucking associations.