What happens when we try to maximize both vehicular access and safety?  We get the minimum width one-way street.

A single one way lane provides total vehicular access, while maximizing the space available for city life.  Minimizing the physical width of the lane increases drivers’ perception of their own speed, allowing them to achieve a satisfying level of driving excitement – at a safe speed.

Single Lane One Way (SLOW) streets have the following special qualities:

1. The intersection of two SLOW streets can employ two squared corners to prevent drivers from accidentally turning the wrong way down a one way street.
2. At the intersection of two SLOW streets, a turning car never has to cross on-coming traffic (which is very dangerous).
3. Passing is impossible, which lowers drivers cognitive (decision-making) workload.
4. Lane switching is impossible, which further limits cognitive burdern, and helps keep traffic “laminar” (slow but smooth flowing).
5. Taxis can be safely boarded from both sides simultaneously.
6. Slower speeds dramatically reduce stopping distance and impact energy (both squarely proportional to speed).
7. Slower speeds work against “induced congestion” while allowing full access for people, goods, and services that cannot be delivered on foot.
8. But: the driving experience still feels fast, because of the trees or solid stone bollards just “inches” away.
9. Less vehicular traffic greatly increases the value and social cohesion of surrounding property.
10. The short crossing distances and slow speeds of a SLOW street make it possible for pedestrians to cross, virtually at will, anywhere along the road.  In contrast, most roads divide the two sides of the street into two independent “half streets“.
11. Minimizing road space maximizes space for trees and #widewalks.

Photo Above:  Av. de Vigo SLOW street in Pontevedra, Portugal.

Two Photos Above:  Nara’s Sanjo-Dori SLOW street (east end).

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Photo Tour, Itami

Below: A photo tour of the SLOW main street in Itami, which connects JR Itami Station to Hankyu Itami Station.  Note the frequent spacing of stone bollards (even between trees), and the #SuperFlat brick pavement, running the full width of the street, facade-to-facade.

Highlighted aerial view below:
– Dark Blue: Stations (Hankyu Itami on left, JR Itami on right).
– Blue Outline: Station Direct Linked buildings.
– Magenta:   Shotengai & Deck Level.
– Green:        Pedestrian/Cyclist only.
– Orange:      SLOW streets (main street running horizontally).
– Yellow:       Sidewalks and #widewalks facing multi-lane streets.
– Red:            Car-centric roads (not easily crossed except at stop light).

Zooming in below on the SLOW street (horizontal orange+green lines), we see that there are no parking lots visible from the main street.  The parking lot at the top is actually on the roof of a building, and the parking lot in the center is smartly blocked off from the main street by the long building highlighted in cyan (Tully’s Coffee and Grazie).

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Note 1) the squared corners of quality 1 are possible at any intersection of one-way streets, but multi-lane streets are wide enough that turning the wrong way is not physically impossible (the squared corners still provide a helpful if less commanding visual cue).

Note 2) quality 6 is sometimes observable on multilane roads, but only at peak capacity.  When multilane roads are below capacity, the physical road width will naturally propel drivers to accelerate.

Note 3) The visually defining features of SLOW streets are: absence of parking lanes, frequently spaced stone/steel bollards, and curbless #SuperFlat facade-to-facade pavement (usually brick, pavers, or cobblestone).  Seen this way, some “One Lane Each Way” streets may qualify as quasi-SLOW streets.  A good example is Chuo-Dori in Nagano.  However, they fall short of SLOW streets in most of the qualities listed above:
1.  Lost.  Cannot employ the squared-off “Nagoya Corner”.
2.  Lost.  Vehicles may need to turn in front of oncoming traffic at intersections.
3.  Passing other cars is only “impossible” in Japan, where traffic rules are strictly followed (and strictly enforced).
4.  Same as SLOW.
5.  Lost.  Taxis can only be boarded safely from one side.
6.  Almost same as SLOW; speeds will not be as slow when there is no oncoming traffic (but still fairly slow, due to the bollards).
7.  Same as SLOW.
8.  Driving doesn’t feel as fast.
9.  Vehicular traffic (noise, etc) about twice as great as SLOW.
10. Lost.  On most such streets, mid-block crossings are unsafe unless usage is limited to buses.
11. Uses about twice as much space as SLOW.