Source: BTS. Transport Canada. Economic Analysis Directorate, adapted from Statistics Canada International Trade Data.
Trade and physical flow imbalances are clearly reflected at major North American modal gateways. Almost all the gateways – land, maritime, and air alike – are characterized by traffic imbalances where inbound traffic far exceeds outbound traffic. This is particularly the case for maritime gateways linked with long distance international trade with Europe and more specifically Asia. The West Coast is notably revealing and is the most imbalanced both in the concentration and the direction of the traffic. Inbound traffic accounts for about 80% of all the traffic handled by ports (a 3 for 1 ratio). The ports of Los Angeles and Long Beach handled 75% of the total freight dollar value brought in through the West Coast. NAFTA land trade gateways tend to be more balanced, but still reflect a negative flow. A surge in oil and commodity prices has increased the share of ports along the Gulf Coast that are focused on energy and raw material trade.
A similar pattern is observed for air gateways, with New York, Chicago, and Los Angeles being the most important. The two largest freight airports in the United States, Memphis, and Louisville, are not gateways but hubs in a national air freight system. Although they handle some international traffic, this traffic is too small to rank these hubs as major air freight gateways. What also characterizes North American gateways is their high level of concentration in a limited number of gateway systems; a set of modal gateways within a relatively defined region that acts as a functional system linking that region to international trade.
| Gateway System | Gateways | Total Share (%) | Imports / Exports ($ billions) 2007 | |
| Southern California | Port of Los Angeles, Port of Long Beach, Los Angeles International Airport, Otay Mesa (Port of Entry) | 17.4% | $329.5 | $108.1 |
| New York / New Jersey | JFK International Airport, Port of New York / New Jersey, Newark Liberty International Airport | 13.5% | $219.2 | $121.3 |
| Detroit | Detroit (Port of Entry), Huron (Port of Entry) | 8.5% | $109.6 | $104.1 |