General Principles for the Design of the Cross-section - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 14

1.2.6 Innovative transport systems
In recent years, the development of guided transport systems for inner city public transport
has been advancing in the Federal Republic of Germany.
Bus transport is being further developed, particularly for travel through tunnels, with buses
being guided electronically or mechanically in the tunnel. The advantage of this principle
is the considerable reduction of the cross-sectional dimensions of the tunnel compared to
a manually steered bus (Fig. 1.10), which can greatly cut construction costs. This type of
tunnel for buses will mainly be restricted to inner-city areas. Bus tunnels are already being
designed and constructed in the cities of Essen and Regensburg. The dimensions of the
tunnel cross-section derive from the size of a standard bus. These have a width of 2.50 m
plus 0.25 m on each side for the rear-view mirrors and a height of 3.95 m. The mechanical
guidance (Fig. 1-11) requires a road trough with a width of 2.95 m.
Figure 1-10 Automatically
guided bus. Circular
tunnel cross-section (left)
and possible cost savings
(right) [168].
Figure 1-11 Mechanical guidance for busses. Rectangular cross-section for straight stretches
of two-way tunnel [15].