S.A.T.U.R.N. S imulation and A nalysis T ools for U rban Automated R apid Transit N etworks.

1. S.A.T.U.R.N.Simulation and Analysis Tools for Urban Automated Rapid Transit Networks.

2. What is Automated Rapid Transit (ART)? • ART refers to the broad class of transportation systems making extensive use of automation to move people or goods. • In this project, we deal with a subset of ART: • Personal Rapid Transit (PRT). • PRT is a relatively new and experimental concept for public transportation.

3. Small Modules • Advantages: • Privacy – Personal Transit • Riders travel alone, or grouped by choice (family or friends, for example). • Fast Acceleration – riders are seated. • Light-weight – 250-350kg loads

4. Use Dedicated Infrastructure • PRT Infrastructure: • Slim, light guide-ways – made possible by light vehicles. • Grade separated, to prevent competition with other modes of transportation. • Narrow rights of way, to facilitate integration into the urban environment. • Network of unidirectional loops provides maximum coverage of the network area. • Bi-directional guide-ways are wider and heavier, which makes them more intrusive. Station design is also significantly complicated by two-way traffic. • Tunnels are also a possibility, though less popular because of higher implementation costs.

5. Off-Line Stations • First, an on-line station: • A typical LRT station is shown. • It is on the main line. • Only one train can pass. • So, an off-line station: • A PRT station is not on the main line. • Therefore, multiple vehiclescan pass the station. Main Line … Train … Station Main Line Station Vehicles

6. Use Off-Line StationsOff-Line Station Design • “SkyTran” puts the main line above the station line. Other designs usually put the station beside the main line. • Incoming modules switch off of the main line and slow down on a deceleration ramp. • Then, they accelerate back to nearly full speed on an acceleration ramp, before merging back onto the main line. • Because modules do not stop on the main line, the average main-line speed is higher.

7. Use Off-Line StationsUsing Off-Line Stations to Improve Performance • Higher main-line speeds are achieved when modules do not stop on the main line. • In an on-line system, the main-line speed drops as the distance between stations decreases (the vehicle must accelerate and decelerate from / to zero, at each station). • As stations get further apart, passengers must travel further to access them. This impacts the quality of service. • Because of their higher main-line speeds, off-line systems can put stations closer together, making them more convenient for passengers.

8. Provide Non-Stop Trips • Non-stop trip: A rider is taken directly from the source station to the destination station. • Contrast with a bus service: • Everyone stops at every stop, even if only one or two people get off the bus. The same goes for a train. • Also, one commonly has to transfer between buses or trains to reach a destination, which is inconvenient. • PRT is more like a taxi service: trips are direct. • Non-stop trips are made possible by off-line stations, because only modules stopping at a given station actually have to stop at the station.

9. Be Demand-Responsive • Contrast: Demand-Static System • Vehicles run on fixed schedules. • Passengers are responsible for meeting vehicles. • So, in a Demand-Responsive System, vehicles respond to trips as requested by passengers. • Again, this is more like a taxi service than what we think of as public transportation. • Off-line stations and small modules make demand-responsive systems possible. • Demand-responsive systems place heavier loads on control systems.

10. Operate using Computers • Control Paradigms: Degrees of Centralization • Asynchronous: anarchy • Synchronous: fully centralized authority • Quasi-Synchronous: somewhere between the two • Quasi-Synchronous control is most popular. • Retains a central authority, but modules have on-board computer systems that enable them to perform some tasks. • We end up with a “constitution” that determines what computers do what tasks.

11. Operate using ComputersQuasi-Synchronous Control • Power-Sharing Agreement in SATURN • Communication distances are limited – e.g. modules communicate mainly with zone controllers near them. • Modules have sensors (radar / IR, etc.) that help it remain safe from unexpected obstacles. Central Computer Zone Controllers Module Controllers Trip Requests Network Health Statistics Module Interaction (Receives input from sensory equipment in nearby guide-ways.) Propulsion System Safety – Checks (Receives input from onboard sensor instruments.)

12. PRT’s Main GoalCompete with the Personal Automobile • Small modules give privacy. • Off-line stations allow for high line speeds (resulting in lower trip times) and closely spaced stations, resulting in higher accessibility. • Non-stop, direct trips make travelling easier and reduce waiting times. • PRT’s demand-responsive nature also reduces waiting times. • Automation allows for high line density (modules can be quite close to one another without jeopardizing safety).

13. SATURN: An experiment in the deterministic simulation of a SMART system. • General facts about SATURN: • Written in C++. • ~ 23 000 lines of source code (including comments). • Fully object oriented design promotes abstraction and code re-use to accurately simulate objects in the system. • Program core is isolated from Windows GUI to facilitate portability. • SATURN is not the end-all of PRT simulators, but it provides a good basis for demonstrating the technology and techniques for PRT control systems and simulators.

14. SATURN: System Overview: Block Diagram Infrastructure User Demand Simulation Demand Coefficients Demand Points Junctions Sections Stations Simulator Programmed Modules Simulator Output Classes System Display Instances Object Display