The sun., 1897-05-06

The four.track tunnel line would furnish
but one track in each direction for rapid
transit, and It becomes \ question for con-
sideration whether the sman addition that
IL would contribute to transportation facil-
titles would Justify the years of time, the
millions of money, the serious engineering
difficulties that would be encountered in
construction, the risk Of danger to gas,
water pipes, and foundations, and the OBJ
struction to the use of highways that the
tunnel scheme would involve.
II, however notwithstanding the serious
objections that exist, tunnel line should
be constructed, there can be no question
that the power used to operate it should be
Independent motors using compressed air.
which are not dependent for the ability to
move upon power transmitted from long
distances but which, by the pure air from
the exhaust, would serve TO some extent as
| an aid to ventilation.
1t is not probable that local travel, which
is the most profitable. would patronize the
tunnel to any extent, for moderate-dis-
| tance passengers would prefer to walk for
longer distances the surface lines, operated
| with independent mechanical power, would
be far preferable; and It would only be for
| long g-distance rapid transit that the tunnel
would be used to any considerable extent.
II any open air system Of rapid transit can
| be devised, even at the Same cost, It would
be preferable; IL at q greatly reduced cost,
there should be no hesitation in regard to
| Its adoption.
The only practical solution Of the problem
| of rapid transit in New York will be found
| in double -decked elevated railroads. The
posts Of the present structure could be in
closed in others much more substantial, and,
| by means Of brackets or cross girders, an
| upper story could be supported. The tr,lsses
on the two sides Of the streets could be tied
together by cross girders, which would
make a rigid structure, and these girders
might, in case Of necessity, be made strong
enough to support one or two additional
tracks for passenger cars or for bicycle
tracks, thus providing for still further
| extension Of facilities in the future, with
out any interruption to existing travel
The upper tracks would be used for rapid
transit and the lower ones for local travel.
The four present elevated lines would ad-
NIT of four rapid transit tracks in each d.
rection. and, by means Of strong cross grid
ers, the number might at some future time
be increased to eight, and, IL still further
extension should ever be required, other
streets might be occupied. Capacious ele-
vators should be provided at the rapid
transit stations, and steps in addition, in
case the elevators should become over
crowded.
Such a system could be constructed with
great rapidity, possibly in one.tenth of the
time required for a tunnel, and its cost
would be comparatively small. Plans for
such double-deck structure have been
prepared by an accomplished engineer
which seem to fulfil every condition.
The only system that can afford one min.
ute headway with high speed and largely
increased capacity is that Of Mr.. ]. V.
MEIGs, for which a charter was granted in
Boston; but this system cannot be applied
to the existing structures in New York.
Skeptical engineers who have taken the
trouble to examine the MeiRs system, have
almost invariably become converts. 1t is
well adapted to rapid transit in Boston, and
IL adopted would give that city the best
system in existence.
Moreover, there arc special dangers and
difficulties to be considered in the con.
struction of the proposed Broadway tunnel.
Here I speak from information contained
in the report of the Board Of Rapid Transit
Commissioners, Messrs. SrEISwAY, SrARIS,
SPENCER. INMAN, and BUsHE, for 1891.
The tunnel in the lower part of the city
cannot be driven through rock, which 10
at many points more than 100 feet below
the surface and at Duane street 1873 feet.
The material is sand, some Of it approach
ing quicksand.
The cost Of the excavation below ground
would be but a small proportion Of the
whole. All the material must be raised to
the surface through shafts opening on or
near crowded streets.
The material is liable to be wet and to
run, and this liability will be increased by
the pressure of Broadway 8 heavy buildings.
Nothing but trial and experience can de-
termine what the extent Of this risk and
damage may be.
A deep tunnel will require elevators as a
means of access, but elevators are not
adapted for large crowds.
A deep subterranean line of transit with
elevators would not attract short-trip pas
sengers, and this business is absolutely
essential for the success Of any line the cost
of which at all approximates that of four.
track tunnel in New York city.
At Canal street new sewers must be con-
structed to carry the drainage east and
west from the tunnel, which will be below
water level at this and other points.
A rock tunnel would be impossible in con-
sequence of the great depth below the sur
face. II the tunnel should be constructed
through the sand, this language is used by
the engineer of the commission, WILLIAM
BARCLAY PARSONS:
while believe that it would DO possible drive
such tunnel also believe that the OF doing SO
would be very excessive and the risk very great. |
The results of the borings show that along large
proportion OF Broadway and especially that portion
where the buildugs the largest and the trafic
greatest the sand 10 exceedingly nne. approaching
not actually Quicksand In the space above the top
OF the tunnel there would DO lying all the water |
mains and sewers. and II the slightest settlement
took place in tho roof OF the tunnel; and in driving
tunnel for long distance through nns sand Il would
be almost impossible to prevent some settlement