NOTABLE ENGINEERING FEAT

Evening Star, Issue 19792, 16 February 1928, Page 15

NOTABLE ENGINEERING FEAT

The Holland tunnel underneath the Hudson River has recently been officially opened, and a stream of motor vehicles is passing hourly through the ■ two tubes which connect Jersey City and New York. It is one of the great- | cst engineering feats of the present j time—ranking with the Panama Canal. | When those concerned with the hand- I ling of New' York’s traffic problem saw j that the bridges and ferries._ were not j enough to take care of the increasing ’ number of vehicles they wondered whe- j thei' it would be better to build a bridge I or a tunnel (says the ‘ Christian Science j Monitor’). A bridge, they found, I would have to be at least 180 ft above : high tide, so that the tall masts of , steamers and warships could go under- 1 neath. This meant that the ap- ; proaches to the bridge would have to | be very long in order to support the weight of such a big bridge, and this 1 meant in turn that the city of New York would have to spend a great deal of money indeed to buy all tho land and material necessary for its construction. A tunnel, on the other , hand, could be constructed in much less space, so it was decided to- build a tunnel. The tunnel itself consists of two parallel tubes or one-way streets far under the water. Four giant burrowing machines worked at the same time, two from the New York side and two from the New Jersey side, moving out across tho river a few inches at a time. With the completion of the tunnel there still remained the important problem of how to ventilate this long roadway. A study was made of underwater tubes in London and other places, but in no one city was there a tube anywhere near the length of this one — one mile and three-iiuarters—nor was there a tube which would take care of the number of automobiles that this one would. So a unique system of ventilation was invented to take care of all the smoke and gases /rom the vehicles and to provide fresh air at all times. Four great power plants were erected, two on each side of the river, and these supply the force necessary to pump the air in and to draw it out. The inside of the tunnel is lined with white tile, easy to clean • and a help in lighting. In each tube are two lines of traffic, with room left on the side to turn out and pass the car ahead. There is a footway along one side, and there are also signal boxes for traffic officers stationed at intervals along the way. Iu the walls are electric lights, which cause no glare and light up the way to such a degree that no headlights are needed on the automobiles. The sliced limit is twelve miles an hour. The Hudson River ferries can take care of 30,000 vehicles every twenty-four hours. It takes at least a half-nour to cross by ferry, and on holidays and Sundays it often takes an hour or more, duo to the number of pleasure vehicles on an outing. Tho tunnel takes care of 46,000 vehicles a day or 3,800 an hour, and with slowmoving trucks in one line and other automobiles in the other the average time to go through is ten minutes. It has taken seven years to construct, and has employed thousands of workmen in the process. It cost nearly £10,000,000.