The diagrams below show bus stop catchments based on a 300m walking distance and a fine rectilinear grid of walking routes (not shown) within one km square blocks for three scenarios of route and stop spacing. (Stops are shown as red octagons, grey shading indicates coverage areas, thicker lines indicate main roads with bus routes, broken lines indicate “mid-block” bus routes, and thin lines indicate roads without bus routes.);
- First scenario; Routes parallel and 1 km apart, stops every 500 m. along each route, stops opposite each other;
- Second scenario; Routes parallel and 500 m. apart, stops every 500 m. along each route, stops opposite each other;
- Third scenario; Routes parallel and 500 m. apart, stops every 200 m. along each route, stops opposite each other;
- As already mentioned above, no crossing bus routes are shown – all routes are assumed to run “East-West”. (Provision of such routes, with mid-block stops, on the First Scenario would increase coverage to 52%.);
- Stops are shown at intersections, as well as mid-block; in practice, while it is desirable to place stops close to intersections for a variety of reasons, they are unlikely to be within 30m of an intersection (measured from the mid-point of the bus stop to the nearest kerb-line of the intersection).
- Having stops staggered from route to route, rather than opposite each other, would improve coverage a little; again however, this would be impracticable;
- A most important proviso: the idealised catchment areas shown make no allowance for any additional walking distance required to cross roads – this can be considerable in cities designed mainly for the car, where multi-lane main roads can be difficult to cross except where specific facilities are provided, and medians may have a pedestrian barrier along them. (Even at intersections where pedestrians are catered for, they may have to wait some time for a green light.)
In the three scenarios, the extent of ground area coverage (within 300m catchment) is 35%, 68% and 90% respectively. It is noteworthy that even with routes 500m apart and stops every 200m, 100% coverage is not achieved – and there is much duplicate coverage. In practice, having stops every 200 metres is not likely to be achievable or desirable, either in terms of finding space for stops on the street, or in terms of being able to run bus services stopping so frequently – unless a “Limited Stop / Local” hierarchy is to be employed as suggested above.
With routes 1 km apart, even if stops were placed 200m apart, coverage would only be increased to 50%. Only by reducing the spacing between routes can reasonable levels of coverage be achieved with fixed-route services.