[Illustration: PROFILE OF BROOKLYN EXTENSION.]

[Sidenote: _Grades and
Curves._]

The total length of the Brooklyn Extension is 3.1 miles, with about 8
miles of single track.

The grades and curvature along the main line may be summarized as
follows:

The total curvature is equal in length to 23 per cent. of the straight
line, and the least radius of curvature is 147 feet. The greatest
grade is 3 per cent., and occurs on either side of the tunnel under
the Harlem River. At each station there is a down grade of 2.1 per
cent., to assist in the acceleration of the cars when they start. In
order to make time on roads running trains at frequent intervals, it
is necessary to bring the trains to their full speed very soon after
starting. The electrical equipment of the Rapid Transit Railroad will
enable this to be done in a better manner than is possible with steam
locomotives, while these short acceleration grades at each station, on
both up and down tracks, will be of material assistance in making the
starts smooth.

Photograph on page 26 shows an interesting feature at a local
station, where, in order to obtain the quick acceleration in grade for
local trains, and at the same time maintain a level grade for the
express service, the tracks are constructed at a different level. This
occurs at many local stations.