Carrier-Track technologies

    

Which carrier-tack technologies will be used for MAIT  ?

Personal Rapid Transit (PRT) Fully automated vehicles. Vehicles captive to the guideway, which is reserved for their exclusive use. Small, light weight vehicles for the exclusive use by an individual or small group traveling together by choice. Small guideways can be elevated or near ground level, or underground. Vehicles able to use all guideways and stations on a fully connected PRT network. Direct origin-to-destination service. Service available 24 hours a day, on demand.

Definition by the Advanced Transit Association, ATRA (see http://advancedtransit.org/)

Higher capacity by reducing headways

Motor-way at its capacity limits$\ldots$

This impressive visual pictures have been scanned form an article by W. A. Wilde [6] and improved by image processing.

$\ldots$ removing the cars $\ldots$

$\ldots$reducing the space between people$\ldots$

    

$\ldots$putting people into PRT vehicles.

Reasons for high space-efficiency of PRT systems      Short time headways (down to fractional seconds). Small required width of track (approx. 1.50-2.00m) Logistics can predict and avoid traffic congestion and optimize traffic flow. Empty vehicles do not require parking space, they can be reused by other passengers.

The carrying capacity, expressed in persons per hour is not an obvious quantity to determine, as it depends on a large number of parameters and assumptions. The prime systematic difference between the manually driven car and an automated system is that the car has a much longer break actuation time. The break actuation time is the time between the occurrence of a breaking manuvre of the preceding vehicle and the actuation of the break. This time is for cars approximately 0.8s and for automatic detection and breaking systems in the range of milli-seconds. The minimum time headway $T_{\min}$, that is the time that passes between two successive vehicles must be [7]

$$T_{\min}=\frac{L}{v}+T_{c}+\frac{v}{2}\left(\frac{1}{a_e}-\frac{1}{a_f} \right)$$

The capacity C_v in vehicles per hour is then

$$C_{v}=\frac{1}{T_{\min}}\cdot 3600$$

The parameters are:

parameter	symbol	value
Vehicle length	L	3m
Line speed	v	10-130km/h
Break actuation time	Tc	100ms
Emergency deceleration	ae	0.9g rubber on asphalt 0.65g rubber on concrete 0.2g rubber on ice 0.5g acceptable without safety belt
Failure deceleration	af	ae if preceding vehicle does emergency breaking $\infty$m/s2 if the preceding vehicle stops instantly

For the first simulation we assumed that the emergency and failure decelerations are a_e=a_f=0.5g. For the second simulation we assumed that the emergency decelerationa_e=0.9g and failure deceleration $a_{f}=\infty$m/s² (instant stop or brickwall). For the car we assumed a reaction time of T_c=800ms.

For comparison, a light rail train system (or metro) with 6 wagons per train and 100 passengers per wagon, where one train arrives each 5 minutes has carrying capacity of 7200persons per hour. However, in contrast with rail, MAIT is a distributed transport network and therefore does not need to concentrate the traffic onto lines. Because a MAIT guideways are smaller and more cost-effective than rail, it is possible to install more tracks to cover a certain area. In conclusion, the capacity of MAIT guideway does not need to be as high as the one of a metro line.

The performance difference between the two graphs is due to different safety assumptions: The second graph shows the performance if present train safety criteria were applied ("brick-wall criteria"). However, excluding the case that a vehicle is able to stop instantly, but decelerates at the maximum emergency deceleration, the throughput of the automated system can be improved considerably as shown in the top figure. In conclusion: safety legislation determines significantly the capacity of an automated network.

Visual impact of PRT-guideways      Options to integrate guideways into the city architecture: Minimization of guideway size. Hide away guideways inside buildings, for example in railway stations, park-houses or shopping centers. Adaption of guideways to city architecture. Secondary use for guideways: elevated guideways could be used as roofs for pedestrian walkways, bike paths, e.t.c. Underground guideways.

Note that unidirectional MAIT guideways have a width of only 1.50m and are comparable in size to larger pedestrian walkways or ``sky-ways''. A city with streets that are protected from sun and rain (such as Bologna, Italy or Bern, Switzerland) is more welcoming to both visitors and inhabitants. Another option are road carriers that do not need any visible guideway and that are slow and can share space with pedestrians. The top guideway photo shows an the ULTra system [8] in an urban environment. The bottom guideway photo (thanks to Dennis Manning) is similar in dimensions to the Taxi2000 PRT [9] system, but this is not an automated Personal Rapid Transit (PRT) system. It is has been built in 1973 by Universal Mobility which was sold to TGI which was in turn sold to Bombardier. In 1996 it was given a refurbishing by Lamoreaux McClendon & Associates. The vehicle is shown in the frame of the lower photograph. Differences between this system and the projected Taxi2000 system:

• Approximately $120 \times 60$cm guideway - Taxi2000 $90 \times 90$cm.
• I-beam columns with exposed parts - Taxi2000 smooth round tapered columns.
• Stark blue and white colors - Taxi2000 muted colors
• Span about 20m - Taxi2000 the same
• Clearance height 4.20m - Taxi2000 the same. European legislation would require 5.70m when traversing roads.

It is hoped that these photos will provide a general idea of the visual impact of a PRT guideway. Photos taken by Dennis Manning 8. August 2000 at CalExpo - site of the California State Fair, Sacramento, California, USA.

Automated Guided Vehicle Systems (AGVS) Properties: Speeds up to 20km/h but walking speed when space is shared with pedestrians. Can use normal road with the appropriate navigation equipment. Useful for highly branched network. Can be used inside buildings. Technical Problems: Safe obstacle detection. Reliable operation in bad weather conditions.

Park shuttle [10] is engineered by Frog Navigation Systems, the Netherlands and Serpentine by Serpentine SA, Switzerland [11].

Future Carrier Technologies high speeds with magnetic leviation (MAGLEV) technology. low energy in vacuum tubes. Space efficient underground transport in tubes.

For more information on advanced transportation technologies, please consult Jerry Schneider's Innovative transportation web site: [12].