The above map, showing the railroad and highway network with points of the top 250 employers in Massachusetts, depicts the methodology for this analysis. First, the transportation generation model utilizes the monocentric city model as a basis. In short, this framework implies that all housing demand in a region will increase with the decrease in distance to the central business district, known as the CBD. Similarly, transportation demand will also be oriented around this central tenant. In order to visually represent this for analysis, I created a multi-ring buffer from a centroid located in Boston's Financial District, which would presumably be the CBD, due to its high concentration of jobs. The rings have a total diameter of 50 miles. Also, in terms of the generation model, the basic assumption implies that every trip generated by an individual has an origin and a destination. Thus, the monocentric city model implies that the CBD will be the highest destination zone during rush hour due to the high concentration of job and commercial activity. 

 

This methodology, although sound in theory, must be qualified on a spatial basis. In terms of the actual rings, they do not have equal areas and disallow for a fully accurate coverage analysis, especially considering parts of the rings are the Boston Harbor. But in terms of classifying the map into origination-destination zones, the rings offer a suitable representation. Although Boston seems to follow this central theory, the location of employment centers outside the CBD must also be considered when assessing the full network. Office parks along roadways like Route 128 and I-95 are common and have an added effect on the flow of travelers.