Page 417 - Shaping smarter and more sustainable cities - Striving for sustainable development goals

 Ducts allow maintenance through their access points. Since access points mostly obviate new
roadway intrusions, traffic delays from duct‐related road works are greatly reduced and avoid
the high cost of surface reinstatement [b‐3]
 Sharing the higher initial installation cost of ducts across all services could make rural service,
and SSC suburbs, more economically feasible. Where ducts are used, all networks are typically
underground in multi‐purpose ducts. Above‐ground electricity and telecom poles are avoided,
increasing safety and reducing natural disaster impacts [b‐3]
 Common utility ducts are designed to accommodate anticipated new and evolving networks [b‐
3] saving the high cost of retrofitting
 An adequate airflow in ducts allows better heat transmission from electricity cables than in
direct trenched/buried situations.

3.1.4 Limitations/disadvantages of Utility Tunnels include:
 High initial construction cost as compared to traditional open excavation methods [b‐1]
 The issue of compatibility between the utilities housed in the tunnel. A defect in one system may
adversely affect the other systems. There has been considerable concern about compatibility
between utilities, issues such as induction between electrical and communication lines, gas
conduits explosion hazards, in‐tunnel temperature rising due to heating and electrical lines.
 The concerns of people entering the tunnels to maintain one service when they are not
experienced in dealing with other types of services (and associated risks) of other utilities.

3.1.5 Resilience and reliability of a common infrastructure

An example of a utility duct with resilience is the Shin‐Sugita Common Utility Duct [b‐6]. To make
local infrastructure more resistant to disasters, such as earthquake, a 220‐kilometer common utility
duct is being planned for the Yokohama‐Kawasaki area in Kanagawa Prefecture. The common utility
duct typically carries many different kinds of utility lines, including gas, electricity, water, sewage
and other types of infrastructure that are indispensable to our daily lives. Once a common utility
duct has been constructed, it is no longer necessary to excavate the street every time something
must be replaced, and the ability to visually inspect water lines etc. greatly simplifies the task of
maintenance. Furthermore, if an earthquake or other major disaster occurs, damage can be quickly
pinpointed and repaired. Where common utility ducts are in place, a city is much better prepared
to deal with emergencies.

GIFT City [b‐2] includes connection to two telecommunications service providers which operate
services in adjacent regions at opposite sides of the city. The advantage of this is that any user can
opt for services from either service provider or both to ensure continuation of service in the event
of a single point of failure.

3.1.6 Provision for multiple service providers

A single authority is needed when a shared infrastructure such as a utility tunnel is to be provided
and maintained.

For example in the new city Lavasa, India [b‐7], a single appointed company establishes and
maintains the assets such as dark fibers, rights of way, duct space and towers for the purpose of
granting rights on lease/rent/sale basis to the licensees of telecom services licensed under section 4
of Indian Telegraph Act 1885 on mutually agreed terms & conditions.

This approach is pioneering as no authority traditionally exists in India to manage cooperation
among utility stakeholders over such a wide range of services.

ITU‐T's Technical Reports and Specifications 407