c There are a large number of joints, including weak insulation joints and the loose joints of switch heels.
d Gauge widening not required by the tangent sides must be provided to secure turnout slack, which causes unstable wheel movement.
Compared to general curves, turnouts have a number of shortcomings including the following.
a There is neither cant nor transition curves.
b Points have entry angles.
c Not enough slack is produced.
As a result, speed restrictions through turnouts are stricter than those for general sections.
Current high-speed turnouts which allow running along tangent sides at 130 km/h have kept the above deficiencies to a minimum. In particular, flexible switches, reinforced guard rails, welding of joints in turnouts and other improvements have been made to remove the running speed restriction on tangent sides.
Replacing to turnout of higher crossing number is the key factor for increasing speeds on the turnout side, but this may prove difficult due to layout problems. Furthermore, high costs have led to the running speed on the tangent side being prioritized. Recently, a #20 symmetrical turnout with a lead radius of 2,151 m was laid using a curve crossing, allowing a high speed of 120 km/h for both sides.
3.5 Strengthening of Inspection and Control of Track Conditions
Now, track inspections are conducted using inspection car and various equipments, the results are entered into a database and analyzed with a computer, a maintenance work plan is formulated, and the required materials and labor evaluated. The computer in these duties has been connected to a network, and both input and output can be performed both at a central location and on site. This represents the situation of track control today.
Inspection technology which has developed is extremely diverse, covering track recording cars (Fig. 6), ultrasonic rail flaw detector cars (Fig. 7), rail tread recorders, joint gap recorders, devices which travel along rails continuously outputting extremely accurate data, measuring devices installed in service trains, human-operated devices which provide data for computer processing, devices which use general purpose measuring instruments, traditional visual inspection devices, and so on.
