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Main Characteristics

Bus-sized or smaller self-driving (autonomous) vehicles

Central control and inter-connected

Battery powered

Rubber wheeled

Closely stacked for high frequency and route capacity

Traverse shared roads, semi-segregated and grade-separated corridors for maximum route flexibility

Why Was This Not Done Before:

New technologies are being developed allowing us to look at new modes of mass rapid transit:

– Driverless operation enables the use of smaller vehicles without the need to employ multiple drivers. Shorter reaction times permit closer stacking.

– New communication systems allow for near instant relaying of information between the vehicles and the central hub.

– Improvement in battery technology now enable electric, emission free, propulsion at lower cost and with longer range eliminating the need for overhead wires for rubber wheeled vehicles thus minimising tunnel height and lowering maintenance costs.

Advantages:

– High flexibility allows the same vehicle to traverse different use scenarios – from sharing existing roads with cars, to semi-segragated corridors with level crossings to grade-separated routes for maximum capacity and reliability. This provides high flexibility in route planning and allows the sharing of corridors with existing modes of transport (eg trams and buses) and rapid system expansion at minimum cost.

– Lower running costs due to driverless operation and electric drive.

– Lower emissions and pollution compared to buses and comparable to rail.

– Only limited driving range is required for battery powered vehicles because drive/charge cycles can be stacked so that all vehicles are available during peak hours but can then recharge in turns during the off-peak. For example, 3 hours running at 40km/h requires 120km (80 mile) range which is easily achievable with current technology.

– It removes the need to run parallel corridors to accommodate trains, trams and buses thus reducing land use and potentially freeing up land for development or enjoyment. In the long term, such vehicles can replace all modes of urban and suburban public transport – buses, trams, metro and suburban rail and offer lower running costs, higher flexibility, similar or higher capacity, lower emissions and higher reliability.

– In the long run, the system would evolve from a traditional line system to more of a ride sharing platform. An algorhytim would pool journeys and passengers between any two stops on the network to remove interchanges. This will require a large network to be built out first and further advances in the self-driving technology to enable the safe use of existing public roads.

Particular Advantages over the Rail Metro Systems:

– Compared to rail, stations can be shorter thus reducing land use and construction costs.

– Much higher gradients and tighter turning circles can be achieved (comparable to buses). At ends, loops can be of lesser diameter.

– Individual vehicles are much lighter resulting in lower breaking forces thus reducing the cost and complexity of all bridge structures.

– Quieter operations allows vehicles to be routed closer to residential properties.

– Depots to be much smaller and can be arranged as multi storey or underground car parks.

– Higher off-peak frequency compared to rail as smaller vehicles are utilised with more efficient running (fewer empty seats). Further savings can be made for low frequency routes by using even smaller vehicles (30 or 50 person capacity) and these can share corridors with longer vehicles as required. This enables lower frequency routes to be maintained in a cost effective manner, or to start small then build up capacity over time. This has always been a challenge for rail systems which require a significant investment in rolling stock to achieve acceptable frequency even when demand is not there yet.

– Better frequency = shorter wait times = lower journey time. More route flexibility = fewer interchanges = lower journey time and less passenger load in stations.

– With smaller vehicles it is easier to fine tune capacity to requirements and respond to changes – e.g. ability to transfer vehicles to another route for big events whilst still maintaining sufficient vehicles on remaining routes.

– Better resilience in case of breakdowns or accidents because vehicles can easily utilise the opposite traffic lane to bypass obstructions. Automatic vehicle control to be utilised to prevent accidents!

– Tunnels can be used in case of emergencies, natural disasters, wars by other road-going emergency vehicles.

– Offer similar or higher link capacity compared to traditional rail metro systems thanks to much closer vehicle stacking afforded by fully automated vehicle control systems and shorter stopping distance. Numerical simulations were run to confirm this.

Disadvantages:

– New and unproven technology requires a leap of faith to adopt.

– The driverless technology is still under development and may not yet be available for use on shared roads. However, the current state of technology can be employed on grade-separated corridors.

– Rail still more resiliant in adverse weather conditions.

– More vehicles do mean more points of failure and potentially lower reliability, although redundant motors, batteries and control systems should be provided to all vehicles to mitigate problems.

(c) Marko Nesovic all rights reserved