Transit Network Map Design
Nothing is more important of a marketing document for a given transit agency than the network map. Yet, many agencies put little thought into the design of the map despite the fact that the map, by showing all of the agency's route "products", is the equivalent of a company brochure showing their product lineup. In this article I examine three traditional models of showing routes on a system map and two recent developments.
Three Traditional Models of Showing the Routes
In the traditional way of showing the routes on a system map, all the lines representing the different routes are drawn the same size. Depending on the model, the lines may be one or more colors.
In the normal model, all lines of a given mode or class of service are given the same color. For example, in the Los Angeles system map, all local bus routes are drawn in orange, rapid routes are drawn in red, and express routes in blue - corresponding to their respective bus liveries.
In the French model, each line is given an unique color. Originally used in the creation of the Paris Metro map, this model is almost ubiquitous in subway maps but due to the much larger number of bus routes in a given city is of limited use in most transit map situations. In fact, it could be argued that the French Model is responsible for the fact that most rail lines have color names (Red Line, Green Line, etc.) and even the rail lines that do not have color names are sometimes referred to by color - i.e. in San Francisco sometimes the Dublin - Pleasanton BART Line is called the "Blue" Line.
In the Dutch model, groups of routes that share a common important corridor or other destination share a color. Applied to Pittsburgh this would mean that the 61A, 61B, and 61C would all share a color because they have an extensive common route segment along Forbes Avenue while 71A, 71B, and 71C would all share a color because they have an extensive common route segment along Fifth Avenue. New York offers a good example of the Dutch Model applied to a subway system, with lines that share a common route in Manhattan sharing the same color designation. Because the shared corridor segment is usually the segment with the most passengers, the Dutch Model can simplify a complex map for passengers by showing them that several routes may be able to take them where they would like to go.
New Approaches to Network Map Route Display
One major critique of the traditional models is that, by giving equal weight to all routes, they communicate that a route that operates every five minutes is about the same as one that operates every hour. Obviously, the more frequently the bus operates the more useful is - a simple fact that until recently was given no consideration at all on system maps. Early adopters of new approaches that take into account the service levels of different routes seem to have taken one of two pathways: the frequent network map pathway, or a pathway in which the approximate service levels of a route are shown through thickness of lines and font size.
The Frequent Network Map
The Frequent Network Map is currently the more popular of the two pathways. In a Frequent Network Map, only routes that operate more frequently throughout the day than a threshold - usually either every twelve or fifteen minutes - are shown on the map. In a nutshell, the Frequent Network Map shows places you can get to without the need to consult a schedule, but by doing so makes the other bus routes seem as though they do not exist. As a result, a reader of a Frequent Network Map who does not live adjacent to a frequent route may erroneously conclude that there is no transit service they can use, even if they live by a route that operates every twenty minutes. Worse yet, a Frequent Network Map draws attention to areas that do not have any frequent service and therefore no lines, and by doing so, may cause the transit agency to incur the wrath of politicians who may believe that their communities are not getting their fair share of transit resources. The fact that Seattle is devoting so many resources to transit expansion in the suburbs despite the fact that the vast majority of ridership occurs in the city of Seattle partially has resulted from suburban politicians deserving what they feel to be a more equal slice of the funding pie.
Varying Line Thickness and Font Size to Show Service Levels
While many transit agencies have used different symbols to denote lines that have abbreviated service spans - i.e. by using a dashed line to indicate peak-hour only service - it was not until the Spokane (WA) Transit Authority's system map redesign that this approach was used in a systematic way. In the Spokane system map, frequent service routes are shown in a thick, red line on the same map as other routes, which are shown in thinner, blue lines. By showing all the routes, Spokane is telling you that the red frequent routes are our best product, but if you need to take them we have other routes as well - thereby avoiding the biggest pitfall in the frequent network map. Another Washington - this time D.C.'s Metro - is in the process of redesigning their maps to reflect the Spokane example, and I expect in the future that the Spokane system map will become an industry best practice. Jarrett Walker of Human Transit is a big proponent of this design.