TOWNS
Therefore:
Build houses into the fabric of shops, small industry, schools, public services, universities—all those parts of cities which draw people in during the day, but which tend to be “nonresidential.” The houses may be in rows or “hills” with shops beneath, or they may be free-standing, so long as they mix with the other functions, and make the entire area “lived-in.”
Z
occasional houses
❖ •$*
Make sure that, in spite of its position in a public area, each house still has enough private territory for people to feel at home in it—your own home (79). If there are several houses in one area, treat them as a cluster or as a row—house cluster (37), row houses (38). . . .
258
between the home clusters and work communities, allow the local road and path network to grow informally, 'piecemeaclass="underline"
| 49- | LOOPED LOCAL, ROADS |
| 50. | T JUNCTIONS |
| Si- | GREEN STREETS |
| 52- | NETWORK OF PATHS AND CARS |
| 53- | MAIN GATEWAYS |
| 54- | ROAD CROSSING |
| 55- | RAISED WALK |
| 56. | BIKE PATHS AND RACKS |
| 57- | CHILDREN IN THE CITY |
| 259 |
| 49 LOOPED LOCAL ROADS** |
|---|
 |
260
. . . assume that neighborhoods, house dusters, work communities, and major roads are more or less defined—local transport
AREAS ( I I ) , IDENTIFIABLE NEIGHBORHOOD ( I 4) , PARALLEL ROADS (23), HOUSE CLUSTER (37), WORK COMMUNITY (41). NOW, for the layout of the local roads.
♦£*
Nobody wants fast through traffic going by their homes.
Through traffic is fast, noisy, and dangerous. At the same time cars are important, and cannot be excluded altogether from the areas where people live. Local roads must provide access to houses but prevent traffic from coming through.
This problem can only be solved if all roads which have houses on them are laid out to be “loops.” We define a looped road as any road in a road network so placed that no path along other roads in the road network can be shortened by travel along the “loop.”
The loops themselves must be designed to discourage high volumes or high speeds: this depends on the total number of houses served by the loop, the road surface, the road width, and the number of curves and corners. Our observations suggest that a loop can be made safe so long as it serves less than 50 cars. At one and one-half cars per house, such a loop serves 30 houses; at one car per house, 50 houses; at one-half car per house, 100 houses.
Here is an example of an entire system of looped local roads designed for a community of 1500 houses in Peru.
 |
| Looped local roads in Lima. |
26 I
Even a simple grid can be changed to have looped local roads.
| J | i 1 | j | i ji |
| *—> | ■ | 1 r | |
| r Irf—1 | Ml | ||
| _^ | ^ j | v. . __ | |
| ’“K I' )l UA way of closing streets to form looped local roads. | |||
 |
| 'Pedestrian paths which go beyond a dead end. |
Dead-end streets are also loops, according to the definition. However, cul-de-sacs are very bad from a social standpoint— they force interaction and they feel claustrophobic, because there is only one entrance. When auto traffic forms a dead end, make sure that the pedestrian path is a through path, leading into the cul-de-sac from one direction, and out of it in another direction.
 |
| These are not Looped local roads. |
Recognize also that many roads which appear looped are actually not. This map looks as though it has looped roads. Actually, only one or two of these roads are looped in the functional sense defined.
262 49 LOOPED LOCAL ROADS
Therefore:
Lay out local roads so that they form loops. A loop is defined as any stretch of road which makes it impossible for cars that don’t have destinations on it to use it as a shortcut. Do not allow any one loop to serve more than 50 cars, and keep the road really narrow—17 to 20 feet is quite enough.
Make all the junctions between local roads three-way T junctions, never four-way intersections—t junctions (50) ; wherever there is any possibility of life from buildings being oriented toward the road, give the road a very rough surface of grass and gravel, with paving stones for wheels of cars—green streets (51); keep parking off the road in driveways—small parking lots (103) and car connection (113) ; except where the roads are very quiet, run pedestrian paths at right angles to them, not along them, and make buildings open off these paths, not off the roads—network of paths and cars (5 2). . . .
263
50 T JUNCTIONS*
. . . if major roads are in position—parallel roads (23), and you are in the process of defining the local roads, this pattern gives the nature of the intersections. It will also greatly influence the layout of the local roads, and will help to generate their looplike character—looped local roads (49).
Traffic accidents are far more frequent where two roads cross than at T junctions.
This follows from the geometry. Where two two-way roads cross, there are 16 major collision points, compared with three for a T junction (John Callendar, Time Saver Standards, Fourth Edition, New York, 1966, p. 1230).
 |
| Sixteen collision points. . . . Three collision points. |
Maps from an empirical study which compares the number of accidents over a period of five years for different street patterns are shown below. They show clearly that T junctions have many fewer accidents than four-way intersections (from Planning for Man and Motor, by Paul Ritter, p. 307).
Further evidence shows that the T junction is safest if it is a right-angled junction. When the angle deviates from the right angle, it is hard for drivers to see round the corner, and accidents increase (Swedish National Board of Urban Planning, “Principles for Urban Planning with Respect to Road Safety,” The Scaft Guidelines iq68, Publication No. 5, Stockholm, Sweden, p. 11).
 |
| Accidents at different intersections. |
Therefore:
Lay out the road system so that any two roads which meet at grade, meet in three-way T junctions as near 90 degrees as possible. Avoid four-way intersections and crossing movements.