The following widths are suggested[225] for parking spaces if in the middle of the street, and parking is at an angle of:
| 90°, | the space should be at least | 15 | feet wide |
| 45°, | 15 | ||
| 371⁄2°, | 14 | ||
| 30°, | 13 |
When the parking space is next to the curb the widths can be reduced 1 foot each. For any angle of stalls between 90° and 45° the parking space width must be greater than 15 feet; for 60° about 16 feet. There are streets where this could be allowed and more machines accommodated than at 45°. Ranking spaces should be marked off 9 feet wide. Some cities have special rules that ranked cars shall stand 6 feet apart to allow any one to get out. The stalls, whether the parking is to be on one side, both sides, or in the middle, should be slanted toward the approach of traffic.
Rotary scheme for traffic around a danger zone where streets meet at right angles.
There is an advantage to parking in the center of the street in that other vehicles may drive up to the sidewalk for loading or unloading passengers. It is objected to, however, on the theory that more space is required for mid-street parking. Where possible parking spaces should be paved with hard surfaces, like concrete or brick. Vehicles parked upon asphalt for a considerable time sink in, and as there is no ironing out by traffic of these depressions the pavement soon becomes rough, retains rain and sprinkling water and rots.
An asphalt strip for driving and a concrete strip for parking is ideal, for this separates distinctly by color the two spaces. On fairgrounds and picnic grounds where many cars are to be taken care of two rows of parked cars are headed together, then a lane and two more rows, another, lane, etc. Parking should usually be at 90° to the lane.
One Way and Rotary Traffic.
—In the crowded cities it has been found necessary to confine traffic to one direction in some of the streets. All streets not wide enough for two vehicles must of course have one-way traffic. Streets a little wider may wish to park or rank cars along one side and have one-way traffic on the other. With parallel streets near together, wide streets even, may be used advantageously as one-way streets with two or more lines of vehicles.
For the convenience of the public clear and distinct signs should be placed at every entrance to a one-way street. Of these more will be said further on.