General Principles for the Design of the Cross-section - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 11

S-Bahn tunnels can have either round, vaulted or rectangular cross-sections. With a per-
missible gradient of 40 ‰ and track radii of R > 250 m, smaller cross-sectional dimensions
are possible than at speeds of over 120 km/h due to the lower design speed. The specified
track spacing is 3.80 m, the distance from track centreline to edge of formation is 3.20 m
and the specified formation width at u = 0 is 10.20 m.
With a clear width of 9.16 m and a clear height 5.49 m, a two-track rectangular cross-
section on a straight line has an area of 50.3 m 2 . In curves, this area is slightly greater due
to the cant. With a clear width of 9.25 m, the Ril 853 specifies a clear height of 5.59 m and
thus a total area of 51.7 m 2 . It is also the case here that the selection of permanent way type
can change individual parameters of cross-sectional design.
One special detail of S-Bahn tunnels is the layout of the clearance gauge for the overhead.
Ril 853.1003 specifies, in contrast to Ril 800.0130, a space to be kept clear for the over-
head as shown in Fig. 1-8.
Figure 1-8 Clearance
gauge for the overhead in
urban rail tunnels.
Figure 1-9 Guideline detail for a two-track S-Bahn tunnel in a curve with rectangular cross-section
according to RiL 853.