PRT FAQ

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1. What is PRT? The best definition of Personal Rapid Transit (PRT) is ‘a transport method that offers personal, on-demand non-stop transportation between any two points on a network of specially built guide-ways’. Other definitions (wrongly) include elements such as vehicle size and elevated construction of the guide-way at times. PRT-like applications deviate from this definition in one or more aspects.

2. What does a PRT system consist of? PRT system consists of vehicles, a supervisory (control) system and infrastructure. The vehicles and infrastructure might be the most visible part of the system, but in the end Personal Rapid Transit is all about (network) controls.

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3. Why should a PRT system be considered for implementation? Personal Rapid Transit combines the positive aspects of the personal car with the positive aspects of public transportation. It thus has many advantages to passengers. It will also have lower operational costs in comparison with a manually operated system with the same service level.

4. O.K. Sounds like PRT is the holy grail of transportation? No. No system is the holy grail of transportation. Personal Rapid Transit is an alternative for transportation within dedicated areas or as a feeder system to existing (public) transportation systems. For every individual application it should be determined which system is the most applicable (please refer to concept applicability).

img_8389 5. What is the vehicle size? The CyberCab accommodates a 6-person family (4 adults, 2 children) and additionally has space available for either a wheelchair or luggage. The vehicle features an automated sliding door and a low floor for easy and level access. A second door can be installed, allowing (dis)embarking on both sides.

6. Is PRT-system electrically powered? 2getthere’s CyberCab is equipped with an electric engine, powered by an on-board energy source. An on-board power source is preferred over power drawn from the infrastructure as this drastically reduces the costs of the infrastructure, increases system flexibility and allows completion of all transports in case of a power failure. The vehicle construction has a modular architecture for energy supply to the electric system, thus allowing the optimal power source to be selected for each application and to be able to adopt any new technologies (e.g. fuel cell). The optimal power source for the application depends on the system configuration (peak-load and duration, charging time ratio), economics and environmental policy. The power source can range from full electric (batteries and/or capacitors) to hybrid concepts (diesel/electric or CNG/electric).

7. What is the ride quality of the PRT system? Ride quality is a combination of comfort, ride experience, level of service and expectancies of passengers. The ride quality is made up out of several elements, belonging to the vehicle, the supervisory control system and the infrastructure. The ride quality was established through tests and several demonstrations (at exhibitions or other events). At each demonstration the crowds’ reactions have been closely monitored, which was very positive, exceeding passengers’ expectations. The vehicles are equipped with suspension according to automotive standards, providing excellent comfort. The vehicles have a gentle acceleration (comfort maximum) and deceleration protocol. The 3-phase braking system ensures braking is always as comfortable as the situation allows. The jerk of the vehicle is controlled by computer and can be adjusted – the jerk is actually maximized on a good comfort level. In the interior all seats are cushioned and supplied with headrests. Space exceeds public transportation standards. Heating and air-conditioning are offered as options for those applications that require it.

img_61498. How is the destination selected? At each station a passenger interface is available. The main function of the passenger interface is to request transportation when there are no vehicles available in the station as the passengers arrives. The request is simply generated by means of a (single) push-button. Passengers indicate their destination on the touch-screen available inside the vehicles; however in those applications where it is required from the throughput of stations, selection of the destination on the station is also possible.

9. What provisions have been taken into account in the design for disabled people? The CyberCab features an automated sliding door and a low floor for easy and level access. It accommodates a 6-person family (4 adults, 2 children) and additionally has space available for either a wheelchair or luggage. The controls in the vehicle are positioned such that they can be easily reached and read by people sitting in a wheelchair.

img_4047 10. How does 2getthere’s CyberCab PRT vehicle navigate? The CyberCab navigates by means of odometry, supported by regular re-calibration with external reference points. Driving and steering encoders on the drive wheels, which provide information on traveled distance and orientation change, support position calculation. For further orientation accuracy a gyro unit can be installed. Odometry is in principal sufficient for accurate navigation. In practice, small inaccuracies occur, resulting mainly from wheel spin and changes in wheel diameter (e.g. due to load variations). These inaccuracies accumulate over the distance traveled, thus creating the need for calibration to correct possible inaccuracies.

11. What other guidance-technologies are applied for PRT systems? Most PRT systems are rail-guided systems (and also draw their power from the infrastructure). The main disadvantage of these systems is the (enormous) costs associated with the infrastructure. The rail-guidance also dedicates that integration of the system at-grade is much more difficult. Guidance by means of walls/curbs adjacent to the track has also been developed. This form is guidance is much more vulnerable (to external influences) and requires higher maintenance and inspection costs. This form of guidance also complicates integration into the design of the environment.

12. What would happen if magnets are not read/missed? It can happen that a magnet is not read or a magnet could be missed. Based on the accuracy of the odometry, a missed magnet will not hinder safe operations. If several magnets in line are not read or missed, the error margin will accumulate. For this reason usually a maximum distance or allowed amount of magnets to be missed is defined, which can differ based on the characteristics of the application and the requirements of the customer.

13. What if an extra magnet is purposely dropped on the road? The calibration is done based on reference points (magnets). All magnets will be detected, but only the readings of magnets detected in the same area as they were expected to be encountered by the vehicle, will be processed and used for calibration. The confirmation of the additional magnet is logged in the on-board computer. All tests (by safety regulators) have demonstrated that 2gettheres’ PRT system is not vulnerable to external influences.

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14. Can the PRT system (or a single vehicle) break down? Any system can break down. 2gettheres’ CyberCab PRT system is engineered to maximize availability and reliability, incorporating 10+ years of experience in the field of automated people mover systems. The possibility of a (system) break down is minimized.

15. What is the availability and reliability of the system? 2getthere has nearly 10 years of experience with automated people mover systems in multiple projects. The people mover systems build on a track record of 22+ years. The reliability and availability have been proven over time, both in people mover applications as well as other environments (e.g. industrial environments). The basis of any design is to maximize availability and reliability, while minimizing the life cycle costs. The FROG-technology is the most sophisticated navigation system available, providing superior reliability and availability. The system has continuous longitudinal and lateral position calculations, ensuring external influences, such as wind, are automatically corrected. The passive reference points merely serve to improve the accuracy even further (<4cm. at 80km/ph).

16. What is the maximum speed of 2gettheres’ CyberCab PRT vehicle? The maximum speed depends on the application and applicable regulations. The navigation technology allows for speeds up to 70 k/ph (45 m/ph) – as demonstrated in the Bus Rapid Transit project Phileas. For the CyberCab the maximum speed will be restricted to 40 k/ph (25 m/ph), although further restrictions can be applicable when it makes sense e.g. from the standpoint of energy consumption minimization.

17. How are obstacles on the track dealt with? Please refer to the section safety systems.

img_4037 18. How is the personal safety of passengers ensured? Personal safety, unfortunately, is becoming an issue for publicly accessible transportation systems in most parts of the world.  The short waiting times at stations of a PRT system contribute to the personal safety of the passengers. The time spent waiting in a station and the chance of unwanted company in the same vehicle is minimized. Although the likelihood is small, additional preventive measures are required.

The CyberCab vehicle design incorporates large (clear) windows, allowing for social interaction between passengers and their surroundings. This is a requirement to enable people to pay attention to anything out of the ordinary. As people are less likely to act nowadays (out of fear) when they do observe harassment or vandalism, technical measures are required. Each PRT vehicle is equipped with at least one camera and an intercom. The camera has a preventive function as images are stored up to 24hrs, allowing identification of perpetrators. However, the images can also be viewed real-time. In the case of an emergency or use of the intercom, the video-images of that particular vehicle will be displayed on the screen(s) of the operator immediately – allowing him to act appropriately. A final technical measure is to install a ‘panic-button’ in the vehicle.

19. What type of communication is used? The preferred wireless-LAN communication system is based on the 802.11a standard that delivers a raw bit rate of 54 Mbps. This system operates in the 5.4 to 5.7 Ghz band and can use 11 independent frequency channels. In case a channel is disturbed or used by other systems, a different channel can be selected. The system is ´hacker-proof´ through passwords, data encryption and IP-address verification. As alternative the 802.11g standard, operating in 2.4 Ghz band can be used.

20. What communication protocol is used? The communication protocol is based on the contention model: a party (the vehicle or the supervisory system ) that wants to send first checks if the communication channel is free. If this is the case it starts sending, otherwise it will wait until the channel is free again. Collisions can occur if two parties decide at the same time that the channel is free and start to send. Received packets are checked for integrity: the actual checksum, packet length, and sequence number have to correspond with the information sent with the package. If a packet is received without error, the receiving party will acknowledge this to the sender. If the sender receives no acknowledgement in time, it will resend the packet (up to a certain number of retries). Reliable two-way communication is thus achieved.

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21. What is the functionality of the supervisory control system? Personal Rapid Transit is all about network (and vehicle) controls. 2getthere’s supervisory control system TOMS features a development history of 22+ years and demanding applications in multiple environments. The experiences with APM-systems ensures 2getthere is technologically ahead of its competitors.

22. On what type of platform is the supervisory control system based? TOMS operates on a Linux-platform on a regular office-PC. All systems and communications are performed real-time, except for the display of the actual position of the vehicles in the layout on screen. It is possible to display the user-interface on a PC operating on a windows-platform.

23. How can I get my layout into the supervisory control system? The routes cannot be imported into the supervisory control system, but it is possible to import the layout of the plant as an aid to marking out the routes (in .dxf format). The supervisory control system includes a layout editor. The routes can easily be modified in this editor.

24. What are the restrictions for the infrastructure? The infrastructure needs to be at least 1850mm wide to accommodate a CyberCab PRT vehicle at 40k/ph. A reduced width is possible at reduced speeds. The system can operate with inclines up to 10%, but in light of passenger comfort a maximum incline of 5% is advised. The vehicles have a narrow turning radius allowing for tight turns.

img_6136 25. Are there restrictions to the environment in which the CyberCab operates? The system operates on a dedicated guide way; the main requirement being space. The system can be installed on different levels: elevated, underground, embedded in buildings and (a-typical for PRT) at-grade. 2getthere strongly believes that the system should be fitted to the environment – and not vice versa. Optimization within the context of an existing environment is very possible due to the flexible nature of the system. For a Greenfield application the system can be integrated within the site in the design process, optimizing system and environment.

26. Is the transportation system environmentally friendly? The vehicle construction has a modular architecture for energy supply to the electric system, thus allowing the optimal power source to be selected for each application and to be able to adopt any new technologies (e.g. fuel cell). The optimal power source for the application depends on the system configuration (peak-load and duration, charging time ratio), economics and environmental policy. The power source can range from full electric (batteries and/or capacitors) to hybrid concepts (diesel/electric or CNG/electric). The main advantage of a full electric system is that it is more environmentally friendly as it has no emissions at the point of operation. The energy requirement of the system is considerably lower in comparison with traditional (manual) transportation systems.

27. What is the advantage of automation? An automated system will have lower operational costs than a manually driven system with a similar service level. Also any mistakes that all human drivers are likely to make (wrong routing, accidents and collisions, etc.) are avoided.

28. Is the PRT system a solution to the current congestion on the roads? PRT is suited for specific applications. Depending on the application it can (perhaps) provide some relief as people decide to travel with (public) transportation.

img_6142 29. Will it introduce a modal shift? 2gettheres’ CyberCab PRT system is specifically suited for local networks – not for long distances. To be able to achieve a modal shift, people need to be persuaded to switch to (public) transportation and leave their car at home. As it is likely that people living in the city al ready travel with (public) transportation (in light of the congestion and parking troubles), the modal shift needs to achieved by convincing people coming into the city from suburbs and other towns to switch to public transportation. This can only be achieved if the transportation chain as a whole is attractive – the chain is as strong as its’ weakest link. If only the last link is improved by installation of the PRT system, but the first link in the chain was the problem (e.g. getting to a railway station), a modal shift is less likely to occur. A modal shift will (definitely) occur if the PRT system improves the (only) weak link in the chain.

30. Does PRT replace our current transportation systems? No. The characteristics of an application (intensity, spacing, spatial planning and the spread of demand) determine which transportation concept is most suited. Each mode has its’ own niche. The CyberCab will function as an additional means of transportation, servicing the veins of the network.

31. Will PRT replace the automobile? No – at least not short term. The automobile provides more flexibility in mobility than any other means of transportation, giving people a sense of freedom. And at this time to many people are in love with their car, taking out their old-timer on a sunny day and cruising over back roads through a beautiful landscape. In the long run the basic technologies now being applied for PRT might be introduced into vehicles. Some day all new vehicles might have the option for automated driving integrated.

32. How realistic is implementation of PRT in inner-cities? Technologically it is possible. However, there are objections against elevated networks in cities. Visual intrusion is a major objection – it would change the face of a city and could intrude in the privacy of the people’s homes. Personal Rapid Transit applications in other surroundings are more realistic short term.

2 Responses to “PRT FAQ”

  1. I’m curious: suppose you would have to mass-produce some 1000 PRT-vehicles for a project. Can you tell me what a vehicle would cost in mass production? Would it be something like 20,000,= or more like 200,000,= each?

    • With the current low volumes of vehicles in applications, all are manufactured by hand. Also the components used, such as the advanced obstacle detection sensors, are not being applied in automotive applications just yet – but will be in the next couple of years. The expectations are that the costs of the vehicles will decrease substantially once larger applications are awarded.

      However, it is important to realize that the costs of the vehicles is irrelevant. It is the costs of the system that matter and should be compared. Vehicles are just one part of the system, the infrastructure and services need to be taken into consideration as well. The infrastructure will normally be at least 50% of the total costs of the system, thus reducing the significance of the vehicle costs. As such 2getthere will only supply information on complete systems to interested parties. As a rule of thumb it can be stated that a system would cost between 8 and 10 million euro per kilometer.

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