Wednesday, October 24, 2012

Transit Station Accessibility

The literature on transit oriented development suggests that pedestrian scale design, a fine-grained street network, and small blocks size are important factors in the importance of transit oriented development. These factors are important because they serve to increase the total area that can be accessed within the typical 'time budget' of a walk trip. The literature on the effects of transit on the building environement indicates that the beneficial effect of proximity to transit extends between a quarter mile and a half mile from the station. At a normal walking pace of 3 MPH that represents a 5-10 walk. However, the distribution of walk trips is not even, but rather follows a pattern of logarithmic decay. The vast majority of trips occurring within the smaller distance, and only a small minority willing to walk the full ten minutes. Thus, the impact of accesibility is more significant in the area adjacent to the transit station. 

--Presuming no obstacles or barriers, it is thus possible to access about 500 acres in a 10 minute walk, or 200 acres within a 5 minute walk. The presence of obstacles or barriers between the transit station and a walkable destination decreases the 'directness' of a route and increases the necessary distance traveled. For a destination on the opposite corner of a block, a pedestrian must travel along the block-face, increasing the total distance by 50%. The larger the block, the greater the amount of distance traveled.--