CHAPTER XXII

CAR TRACKS

It was pointed out in Chapter IV that, from the standpoint of the highway, the location of car tracks within the limits of the carriageway is accompanied by several disadvantages. The progress and development of communities, however, are dependent to a large extent upon the systems of transportation between them and the surrounding districts. Street railways and motorbuses are the two systems which must be considered in designing the highways. Although it is reasonable to expect that in the future motorbuses may replace surface railways in many instances, it is extremely doubtful if in the near future their use will ever become so common that transportation by electric traction railways on the roads and streets will be entirely eliminated. The problem, then, is to construct the railways so that all of the advantages can be enjoyed and all of the disadvantages will be reduced to a minimum. This will involve a consideration of the location of the tracks and details of track construction.

LOCATION. There are several advantages in having the car tracks located on a part of the highway which is inaccessible to other traffic. This arrangement does not interfere with the convenience of those entering and leaving the cars and has the added advantage that the cars can be operated at higher speeds without danger to other traffic. The work incident to the maintenance of the tracks can be carried on without disturbing the surfacing of the carriageway, and obviously since the tracks are without the carriageway the wear of the latter is not affected by their presence. From the standpoint of the traction companies several advantages may be noted. The cost of the original construction is generally much less than where the tracks are located within the carriageway due to the fact that the

special methods of construction necessitated in this last instance are not required. The expenses of maintenance are also smaller than where the tracks are so situated that they can be occupied by all kinds of traffic.

The arrangement, which is above described, may be accomplished sometimes in cases of wide residential streets or boulevards, where the tracks may be located either at the sides or in the center of the highway. There are very few instances in cities of this country, however, where this arrangement is carried out except in the case of boulevards. The common arrangement is to have the car tracks located within the carriageway, either in the center or at the sides, the tracks being made flush with the adjoining pavement so as to offer as little obstruction as possible to the other traffic on the highway. Whether the tracks should be located in the center or at the sides is dependent, of course, upon the local conditions, but primarily depends upon the width of the carriageway. The same general principles govern, regardless of whether the location of tracks in a street or a road is being considered. In Chapter IV the New York City ordinance was quoted as requiring a minimum width of roadway of 30 feet for streets in which there is a single track railroad and 40 feet for those in which there is a double track railroad.

While local conditions determine in each case what the best location is, the following information will be of assistance. The width out to out of cars varies from 8 feet to 9 feet 1 inch. The clearance allowed between passing cars on a double track is variable, depending somewhat upon the speed. It is generally a minimum of 5 inches and may be as much as 2 feet on very wide streets, where there is plenty of room. The track gauge in this country is almost universally made about 4 feet 811⁄2 inches. In Europe there are several instances of railways with much narrower gauges, sometimes being as small as 2 feet 6 inches. If a standard gauge is used and a minimum clearance, the distance center to center of tracks for the widest cars will be 9 feet 6 inches and the total width out to out of cars on the tracks will be practically 14 feet.

TRACK CONSTRUCTION. Experience has shown that the maintenance of a road surface adjacent to a car track is more costly than it would be if the track was not present. It is the opinion of some engineers that the greatest enemy to a railway is not the cars or the vehicular traffic, but water, and from its effects is attributable 90 percent of the maintenance charges. The water seeping down by the rail, particularly at the joints, softens up the underlying soil with the result that the track pumps and the adjacent pavement are soon disintegrated. Sometimes the surface of the rail head as it comes from the rolls is more or less uneven and wavy. The treads of car wheels soon get worn uneven, and this together with the unevenness of the rails, produces vibrations which are very injurious to the adjoining pavements. Some lateral thrusts are also developed as the cars proceed along the tracks. Sheet asphalt and other

types of bituminous pavements are particularly susceptible to a very small movement of the rail both laterally and vertically.

Rails. It is interesting to follow the development of the present types of rails used in street railway construction. Among

the earliest types was a flat stepped head which was spiked to a wooden stringer, the stringers resting on wooden cross ties. The traction companies in those times were not obliged to build their tracks so as to obstruct the other traffic on the carriageway as little as possible. In fact, one type of rail was developed for use in New York City, which was designed with the intent of being so objectionable that the vehicles would keep off of the car tracks. This, like the first rail described, was a rail head which was spiked to a wooden stringer. Instead of being a stepped head, however, with one side flush with the pavement, the rail head projected above the surface of the surrounding pavement in the form of an inverted U, the car wheels having a center groove. The railway companies soon appreciated that more permanent construction was necessary, and many types of rails were developed in which the head could be removed when worn and replaced with a new piece, the web and rail base remaining permanently in place. Stepped heads and those with a groove similar to the ones in use to-day were also tried.

-6"

FIG. 213. T-Rail.

The types of rails encountered to-day are the grooved rail, the stepped rail, and the T-rail, as shown in Figs. 211, 212, and 213, respectively. When the car track occupies a space inaccessible to other traffic it is quite customary to use the T-rail. Although this form of rail is also adopted sometimes for track construction within the carriageway, special means are taken to form a groove so that the result, as far as the traffic is concerned, is practically the same as if a grooved rail had been used. A rail with a stepped head has been commonly used, but offers considerably more obstruction to traffic than a grooved rail. The smoothest track from the standpoint of other traffic crossing over it is without doubt constructed with grooved rails. This

type is now being largely employed both in this country and in Europe. There are several forms of grooved rails in use, the principal variation being in the position of the inside lip with reference to the tread and the shape of the groove. In some types this lip is short and the inside edge is below the plane of the head, while in others it is wide and ends in almost the same plane as the tread part of the rail. Rails are made of different depths, varying from about 4 to 9 inches. The 9inch rails are generally designated as girder rails. A rail of this depth is required if any form of permanent pavement such as wood block, stone block, or sheet asphalt, etc., is to be built next to the track, in order to give sufficient room for a good thickness of concrete over the tie to support the pavement above.

Rail Joints. The weakest point in the rail is the rail joint. It is customary to form the joints with splice bars, similar to those used on steam railroad tracks. Rail welding, which not only makes a more permanent track, but also makes the rail a better conductor for the current, is gradually replacing this form of construction in the best practice. When the welded rails are imbedded in the surrounding pavement they need no provision for expansion and contraction, since changes in temperature simply develop some stress in the rails.

Foundation. The simplest form of track foundation is that of imbedding wooden ties in a bed of gravel or broken stone. This method is ordinarily used for tracks constructed on highways outside of built-up districts, for tracks on streets that are not surfaced with a permanent pavement, and fort racks that are built on a right of way which is inaccessible to other traffic. When the tracks lie within the carriageway and are flush with the surrounding surface, this type of foundation may be used if the surfacing of the adjacent carriageway is of macadam. The maintenance expenses for the surfacing even in this case, however, will be greater due to the presence of the track.

It is absolutely essential in track construction which is flush with the roadway and adjacent to pavements of wood block, granite block, brick, or any form of bituminous pavement to