Environmental Engineering Reference
In-Depth Information
developer invests fully in development, as long as there is no market for the end
product
[12, 13]
. Only one system has been fully implemented (1972, in Morgantown,
West Virginia). It has successfully demonstrated the viability of key PRT technology
components, including off-line stations, on-demand service, nonstop origin-to-
destination transport and fully automated control systems
[14]
. Since it began
operating, the system has demonstrated very high reliability of 98% or greater.
The fundamental elements of a PRT system are:
On demand, origin to destination direct service
: the service is
available on
demand
rather than on fixed schedules. In most cases a pod will already be at the
station,
available 24 h a day
at all stations on the network to
meet individual travel
needs
. Its size allows for the passenger to choose to have his or her own ride. Non-stop
travel service ensures
short trip times
(the stations are placed off of the main guide-
way). In this system, traffic is adapted to the passenger, instead of the passenger
having to adapt to traffic - and that is what makes the difference
[15, 16]
.
Small, fully-automated vehicle
: PRT vehicles are intended to operate under com-
puter control and require no operator or driver, which considerably lower operating
costs. The system will automatically route the vehicle to the desired destination
within the shortest possible time and without the need for further user interaction
with the system. Operations involve staff to support central control, network man-
agement and vehicle flow systems, maintenance, security, and station services
[16]
.
Due to the need to provide a high degree of safety, speed and accuracy to effectively
manage potentially large fleets of vehicles over complex networks, PRT networks
have a number of unique operating and control system requirements.
Exclusive-use guide ways
: designed as elevated systems with beams and support
structures sized for lightweight two-four passenger vehicles. The light weight of
each vehicle allows for economic construction of the guide-ways, and less land-use.
PRT systems use networked and separated guide ways to permit higher transportation
capacity and safety levels as the system will not interfere with current modes of
transportation
[17, 18]
.
Off-line stations
: these are a major breakthrough, designed with a “siding” track
or guide way. Vehicles not stopping at a particular station can bypass that station
and are not delayed by other vehicles boarding and alighting passengers; the PRT
station should be sized according to the necessary number of loading berths needed
to handle the demand at each station.
Low-emissions and resource efficiency
: electric power is used primarily for pro-
pulsion and vehicle amenities. Beyond the need for propulsion, a PRT vehicle needs
power for on-board systems and passenger comfort. It should support limited
HVAC services as well as vehicle control and communications. The electric power
can come from many different, preferably renewable sources (Fig.
2
).
Some power is used to move around empty seats. With PRT, empty vehicles are
sometimes routed to another station with a higher demand.
Figure
3
shows that the power required per seat to move a PRT pod is very low
compared to a bus or a car. The efficiency of the system depend on many other
factors, most of all on the occupancy of the vehicle
[19]
.
Vehicle and Passenger Accommodations
: for urban environments, studies have
shown that the typical private automobile has 1.63 occupants for all trips, 1.14
