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:

1. Must provide mixed-use characteristics - accommodate freight, mass transit and personal vehicles
2. Must have guideway speeds that have a constant velocity - guaranteeing reliability of travel times with traffic flow control and excess capacity designed to prevent impairment of the constant velocity feature (intercity speeds of approximately 130 mph, urban highway equivalents at 65 mph, urban arterials at 32.5 mph, and neighborhood local guideways at 16.25 mph; urban bypass routes could maintain 130 mph; vehicles may move in platoons [groups of 5-10] with 100 to 150 ft between platoons);
3. Must be capable of modular, incremental acquisition and be scalable to a national network;
4. Must be able to accommodate those with disabilities;
5. Must have safety that is better than automobile statistics - reduce high speed crashes to less than 5 percent of current highway performance for traffic converted to guideway;
6. Must be designed so that the reliability of vehicles on the guideway system renders the probability of breakdowns on the guideway to the range of 10 to 100 disabilities per 100 million vehicle miles with clear strategies for removal of disabled vehicles and their occupants;
7. Must be economically competitive with an evolving baseline design of internal combustion engine/electric hybrid automobiles.

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