Proposed system requirements for the design of a dual mode transportation system
This is a slightly edited version of an excerpt from the
CEETI study, by Christine Ehlig-Economides and Jim Longbottom, of dual
mode transportation, published in May, '08 by the Texas Transportation
Institute of Texas A&M University, pages 31-32. It has been rearranged
into two categories, Musts and Shoulds
From the literature a list of system requirements for a dual
mode transportation architecture was developed and is summarized as follows.
The system:
Shoulds
1. Should use zero or ultra-low emissions vehicles;
2. Should be user scheduled - efficient and accessible 24/7/365, on demand;
3. Should have throughput capacity of vehicles at least four times that of conventional
highway lanes in the urban environment and eight times that of conventional
highway lanes in the intercity environment - this requires short headway
between vehicles and may dictate a requirement for more than tire/pavement
frictional braking capabilities for emergency use;
4. Should have direct origin-to-destination service with no intervening
stops while in automated guideway mode;
5. Should have an elevated or underground guideway to avoid at-grade
conflicts and minimize right-of-way requirements and noise/visual footprint
of the system;
6. Should be compatible with remote automated parking systems;
7. Should be capable of single mode PRT operation for people movement and
be cost-effective for low/medium density population areas (2,000 to 2,500
persons/square mile;
8. Should be capable of operating in an automated (driverless) mode while on the guideway;
9. Should preferably have public-private financial backing for the new
system - users repay capital, operating and maintenance, energy costs, and
financial return to investors;
10. Should maximize the use of existing rights-of-way and interface to
adjacent conventional roads in a seamless manner;
11. Should provide security and privacy for individuals or small groups
traveling together by choice - door-to-door service in the same cabin;
12. Should have an evolutionary path to the final network vision that is
plausible - perhaps PRT/mass transit in urban areas and a
terminal-to-terminal captive system for freight with later ability to join
mass transit systems and freight links to create a full network, accessible
to private dual mode vehicles;
13. Should have a guideway design that is modular to facilitate factory construction
and on-site, easy assembly/replacement and accelerated build time with
minimal disruption to adjacent activities;
14. Should consider a triple lane guideway - one in each direction and the
middle one for diverted traffic in event of maintenance/repair/contra-flow
needs;
15. Should be able to accommodate cars of approximately the size/shape of today's
conventional cars and about a 3,000 lb load per vehicle including vehicle and
occupants (freight vehicles to handle two pallets with about 2,000 lb
per pallet and allowing about 2,000 lb vehicle weight, two pallet
sizes/shapes to fit within 5ft x 5 ft x 10 envelope; actual size and weight
limits are to be optimized and negotiated through competitions and impact
analyses);
16. Should be designed for all-weather operation without impact to
performance or safety;
17. Should use vehicles that use stationary electric grid power while mobile
on the guideway;
18. Should enable terminal-to-terminal automated/driverless freight
movement;
19. Should have a guideway that optionally provides hardened infrastructure
for electrical conduits and communications cables.
Last modified: June 15, 2008