Evening star. [volume] (Washington, D.C.) 1854-1972, 1931-02-15
HOLLAND TUNNEL GIVES AID
TO TRAFFIC CONDITION STUDY
Observation of Number of Vehicles Nov
ing in Lanes During a Specific
Time Is of Value.

rs feet apart through the fast lane
the trip through the tunnel, from West
to the East portal Ca distance OF 1871
feet), was made 100 seconds, which
was at the rate of ass feet per second
or 316 miles per hour.
The westbound trip 8,557 feeO was
made IN I'll seconds, or at the rate Of
so feet per second or "a miles per hour
There was less traffic westbound at this
time of day than eastbound, hence
the greater possible speed.
The trip eastbound in the slow lane
required 378 seconds, which is equiva-
lent to an Average of 22.1 feet per
second or ISL miles per hour. The west
bound trip in the slow lane required
$50 seconds, equivalent to 24.4 feet per
second or 1877 miles per hour.
An examination of the speed curve
shows a considerable variation in the
speed in the tunnel. The average down.
grade speed and the speed on the level
was considerably greater than on the
upgrade after passing under the river.
This change in grade (about 312 per
cent? Is almost imperceptible to the un-
observant driver. The average driver
especially the truck driver fails to
accelerate on approaching the grades,
and this has a tendency to slow down
the whole line. At one time on one
of these up-grades in the slow lane the
speed curve shows that we were NOV
ing at little less than miles an hour
On the assumption that all cars
in the fast lane, eastbound, maintain
an average speed Of 46.5 feet per second
or 31.7 miles per hour, and that the
cars maintain an average distance apart
of rs feet or 90 feet, center to center,
the tunnel will clear itself of SO cars
20 times an hour, which indicates a
maximum capacity Of 1850 cars an
hour.
On the same basis, the eastbound fast
lane clears itself Of IS cars 81 times
an hour, which indicates a maximum
capacity of 1895 cars an hour.
Slow Lane Capacity.
The capacity of the slow lane on the
same basis but at a speed of 21.1 feet
per second or Is miles per hour, would
be 883 cars an hour. If the distance
maintained between the cars, center to
center, were so feet the capacity would
be approximately 1920 cars an hour
and If the distance between cars, center
to center, were only IS feet the capacity
at is miles an hour would increase to
1857 cars an hour. None Of the maxi
| mum capacities has ever been reached
in actual practice.
On May 80, 1880, from to am,
the westbound tube cleared 2,507 cars.
This being a holiday, it was assumed
that there was little, If any, truck
traftlc and that each lane carried 1883
cars in the hour.
On November 20, 1927, a total of
2,450 cars cleared the eastbound tube
in one hour. This also being a Sunday,
both lanes were fast and, therefore,
averaged 1,225 cars per lane per hour
The greatest number of cars yet to
pass through the tubes in given time
appears to hive been on August 8, 1890,
between 80 and 2 pm. The fast
lane carried 701 cars and the slow lane
260 cars in the half-hou period, which
is equivalent to 400 cars an hour in
the fast lane and $50 cars an hour in
the slow lane, or a total of 1922 in
both lanes.
There are two possible reasons which
may account for the fact that the
tubes have not yet operated to their
maximum capacity. One Of these may
be attributed to the delays incident to
the purchase and collection of tickets
and to the weaving of traffic from
several lanes into two lanes as to enter
the tunnel. The other reason may be
due to the fact that some drivers, not
approaching the change in grade, fail
to accelerate or to maintain a uniform
speed, thus slowing down the entire
lane and cutting down the possible
capacity.