Boston.In Boston * the crown per foot of half width of the pavement is as follows: macadam, inch; granite block, j inch; sheet asphalt, asphalt block, or brick, 6/16 inch. On side-hill streets the maximum difference in elevation between the crown and the pavement next to the curb is as follows: for macadam, inch per foot of the half width of the pavement; for granite block, 3/4 inch per foot; and for sheet asphalt, asphalt block, or brick, 34 inch. If there are one or more street-car tracks on the street, the above crown is obtained at the rail nearest the curb.
Chicago.In Chicago § the standard crown for asphalt, brick, or granite block, is a minimum of 2 per cent and a maximum of 5 per cent of the half width; for macadam, a minimum of 4 per cent and a maximum of 8 per cent.
Omaha.In Omaha the crown is decreased as the steepness of the crown increases, a method which is commendable. The crown
for asphalt is: C= w (100— 4p) ÷ 5,000, in which C = the crown of the pavement in feet, w= the distance between the curbs in feet, and p= the per cent of the longitudinal grade. For brick, stone block, or wood block, the crown is five sixths of that for asphalt. A formula for crown formerly used in Omaha gave a less crown than the above rule for brick, stone block, and wood block, and as much less crown for asphalt. The former formula is: for brick, stone block, and wood block, for sheet asphalt Notice that in the i ties mentioned above asphalt has the smallest crown of any form of pavement, except in Omaha, where it has the largest. Considering only the smoothness of the surface, it appears that asphalt should have the least crown; but consid ering only the fact that asphalt rots when continually wet, it appears that asphalt should have a large crown.
The above rules for crown must be modified somewhat when the two sides of the street are not at the same elevation— see § 488, page 328.