For track in pavements the rails may be laid to close joints, no allowance being necessary for change of temperature when the rail is fully bedded- in the pavement.
A number of modifications of the above joints have been devised, some of them passing under the base of the rail and supporting it on the tie. Electrically welded or cast joints are also sometimes employed, consisting in welding a bar of steel on each side of the end of the rail, or in casting an iron block about the ends to be joined, the casting being joined by means of the holes through the web of the rails.
Where chairs are employed to raise the rails above the ties, joints are frequently most satisfactorily made upon long chairs or bridges reaching across the space between two ties and forming a firm bearing for the ends of the rails.
In order to facilitate keeping the joints tight and enable the bolts at the rail-ends to be screwed up without taking up the pavement, joint-boxes are sometimes employed. These consist of openings with removable covers, giving access to the bolts at the ends of the rails.
On curves, guard-rails are commonly employed. Where tee rails are employed the guard is usually a second rail placed on the inside of the main rail, leaving only room for the wheel-flanges. In some instances, however, the guard is formed by bolting a flange to the main rail. For girder rails the guard is usually formed by the use of a rail in which the groove is wider and the lip heavier than common, and sometimes the lip extends somewhat above the head of the rail. Any difference of elevation of that kind is objection able as producing unevenness in the pavement, but is frequently used as essential to the proper operation of the cars upon the curves.
Pavement in Car Tracks. The wear of a pavement is usually considerably increased by railway tracks upon the street. The extent of this wear depends upon the nature of the paving surface as well as upon the construction of the track. It is mainly the differ ence in resistance to abrasive wear between the rails and the paving surface which causes uneven and more rapid wear of the pavement in vicinity of the track.
A broken-stone surface, on account of its rapid wear, is particularly objectionable along a line of track, and is very difficult to keep in proper surface.
In case of narrow streets or rough side-pave ments the use of the track for hauling heavy loads causes the cutting of the pavement upon the outside of the track, due to the gauge of trucks being greater than. that of the track. This is especially the case where, owing to the use of side-bearing or center bearing rails, the flange-grooves are wide enough to permit the wheels of trucks to enter them.
' Where tracks follow country roads it is usually desirable, if possible, to place the track at one side and leave the center of the street free for the use of the ordinary traffic. When a broken-stone or gravel surface is employed it is common to lay planks on each side of the rail and bring the pavement against the planks, which materially lessens the obstruction offered to travel by the rails, as well as the difficulty of keeping the pavement in surface.
The methods of placing pavements in tracks depend upon the shape of the rail-heads and have already been discussed. Under heavy traffic when asphalt street surface is employed it is quite common to pave between the rails with stone or brick, and often to put a toothing of the same material outside the rails adjoining the asphalt. This serves to prevent the cutting of the asphalt along the rails. Sometimes when stone blocks are used in track the concrete base is omitted and the blocks are set on a gravel or broken stone base. When such construction is employed the track should be very carefully ballasted and brought to an even bearing. There is always a tendency for the track to work loose from the pavement and get out of surface, and under heavy traffic very firm con struction is necessary to counteract this tendency.