The extent of the market area of an inland freight distribution cluster is related to the supply chains being serviced as each supply chain has different requirements in terms of lead time as well as the volume and frequency of deliveries. Many supply chains, particularly in retail, rely on daily deliveries, implying that the market area is mainly a function of the average length of domestic truck freight haul, which is around 500 miles (800 km). An approximate way to assess market accessibility relates to a simple Euclidean distance radius. Thus, 500 miles is considered to be the upper limit of an operational daily radius for trucking, although shorter distances are generally preferred. 500 miles acts as a proxy for travel time, but a day of trucking can vary depending on the congestion level, which also has an impact on the reliability of deliveries. Additionally, new safety regulations for trucking are being implemented in the United States since 2008 (CSA; Compliance Safety Accountability) and which will impose more stringent monitoring of driving hours. The likely outcome is a reduction in the average length of domestic truck hauls.
On the above map the share of the total American population within a 500 miles radius from each major freight distribution cluster is depicted. From this standpoint, the optimal location (points of highest accessibility) is in the vicinity of Columbus, Ohio with 47% of the US population accessible within a day of trucking. Most locations within the Midwest have a share above 35%. Still, since a significant share of retail goods are imported through container ports, it is important to also consider port throughput as a factor in concordance with market accessibility. It underlines the difference between regionally anchored and long distance logistic functions. For instance for Los Angeles / Long Beach, only 15% of the US population is within 500 miles while for New York this share is double (30%). Thus, a great share of the logistical activities performed at LA/LB concern long distance freight distribution along the Los Angeles / Kansas City / Chicago rail corridor as the regional market is not large enough to support such a volume. This involves for instance an active transloading function where the contents of maritime containers are transloaded into domestic containers. For New York, more than 80% of all the traffic is bound to the immediate hinterland, implying that transloading is less prominent since most maritime containers will be brought directly to the customers. On the Canadian side, the two most important container ports stand at two extremes; Montreal covers 23% of the American population within 500 miles while Vancouver covers only 4%.
The importance of freight distribution cluster along the US-Mexico border is under represented on the above map. For instance, Laredo is within reach of major Mexican population centers, such as Monterrey.