It is aimed to improve the line speed over this route. Thus it is especially beneficial to identify and elaborate the key track design issues required in the redesign process. These design issues include route surveying, track components identification, curve track requirements and other factors beneficial for the railroad redesign development.
Route surveying is done to acquire necessary data for the proper placement of grades, bridges, culverts, and curves in a railroad system. The usual route surveying can be done traditionally or electronically. Traditional route surveys employ 'differential levelling, taping manually scribed data, cross sections and baseline-referenced topography'. Electronic survey on the other hand, make use of 'total station, data collector and computer technologies' for field data acquisition and manipulation. (Engineering Policy Group, "Route Surveying," par. 1, 2)
The Swiss Trolley, 'a multi-sensor measurement system incorporating real-time kinematic (RTK) GPS' has been used in the United Kingdom for precise and accurate rail track surveying. This rail track surveying system is essential in the redesign and renewal of railroads because it provides 'dense and accurate track information' which assures a 'precise description of the actual physical track'. (Glaus et al. par. 1)
Route Improvement Components
Rail track supports the train weight, tractive and braking forces, and lateral forces from guiding the wheels. Thus it is vital to choose and use rail components that are 'suitable for the proposed duty and fit the purpose'. Rail size must be selected correctly (see Figure 2); and methods of joining rails can either be Thermit (aluminium oxide) welding or 'huck' bolts together with standard fishplates. Rail-to-sleeper fastenings must provide resistance to the 'overturning force on the rail and lateral steering forces on curves' and should maintain gauges. In the United Kingdom, 'surface mainline tracks usually make use of tapered baseplates (Figure 3 & 4) to counteract these resistances. (HSE, p. 5, 11 pars. 1)
Figure 2 Common Rail Sizes and Dimensions According to BS 11: 1985.
Figure 3 Baseplate
Figure 4 Baseplate Assembly
Ballast and Drainage
In order to guarantee superior quality track, proper ballasting is crucial. According to HSE (p. 14) ballast installed in rail tracks must fulfil the following purposes:
Transferring the load to the roadway floor;
Holding the sleepers in place;
Allowing water to drain; and
Permitting the regarding of track.
It is essential for ballast to 'not crumble under load or wet conditions' and 'should bind together as a mass when laid, but ought to retain its open structure to allow drainage'. Usually the ballast size used is 28 mm single sized for high-speed tracks. Granite ballast is resistant to wear and tear thus provides durable rail track ballast. (HSE p. 15)
There is an increased production of forces when a rail vehicle travels around a curve; these forces boost the wear and tear on the track and amplify derailment occurrences. Thus it is essential to design curves to minimise these drawbacks. The following are therefore required for a curved track:
Maximum practical radius;