The traditional “grid” pattern of streets and blocks has historically dominated roadway development in large city centers. Optimal block dimensions range from approximately 200 feet to 600 feet on end, forming square or rectangular shapes, which generally accommodate efficient vehicular and pedestrian circulation patterns. The City of Columbia consists of square blocks approximately 600 feet on end.

Because of the heavy emphasis on pedestrians and street-front retail characteristic of most large cities, the ideal roadway components of downtown “park-once” districts are: two to four lanes of two-way traffic; wide sidewalks (10-20 feet); and on-street (parallel or diagonal) parking. 

Although two-lane sections are optimal because they encourage slow speeds and minimize the pedestrian crossing distance at intersections, well-designed four-lane sections—often deemed necessary to adequately handle heavier traffic volumes—are also acceptable. The importance of two-way traffic is that it discourages high vehicular speeds while ensuring that street-front businesses maintain maximal visibility and accessibility. On-street parallel or diagonal parking maximizes access to street-front businesses while also serving as a “buffer” between pedestrians and moving traffic.