What is the purpose of Dual Mode?

by Palle R Jensen, RUF International

A Dual Mode system should not be proposed because a new technology becomes available. It should be proposed if it can solve some real transportation problems.

In the following I will try to explain how the RUF concept has been developed from its creation in 1988 (published for the first time in 1990).

As a professional inventor, I found it very frustrating to listen to the endless fight between car supporters and train supporters. The debate was very bitter and not constructive. At that time I had earned some money on another invention (laserscanner), so I could use some time to "rethink transportation" without having any funding to support it.

My analysis showed that it would be a major advantage, if it was possible to combine the flexibility of the car with the efficiency of the train. The thought of Dual Mode was borne in my mind. Later I found out that many other people had already had the same basic thought. Being unbiased by others ideas, I came up with my own system design: the RUF concept (RUF = Rapid Urban Flexible).

What is good about the traditional concepts:

Trains have high capacity and low environmental impact, but passengers have to enter at stations and to adhere to the time table.

Cars are fast, flexible and attractive, but they take up too much space and they use too much energy.

What is bad about the traditional concepts:

Trains have poor brakes and since they normally run at grade, they represent danger for people and animals. The poor brakes mean that safety distances have to be long so frequent departures are impossible.

Trains can derail and the driver can get tired and inattentive with severe consequences.

Cars require the constant attention of the driver. Even a very skilled driver can be injured by a bad driver. The situation is extremely risky. The lateral guidance is critical.

Cars use much space, mainly because the braking distance increases with the square of the speed. This spacing is controlled by the individual driver who has limited knowledge about the situation further ahead. This factor causes chaotic behavior in the flow of cars. Congestion is the result.

Cars use much energy and pollute locally. Air resistance at high speed and stop-and-go traffic at low speed are the main reasons. Noise is a big problem.

Gradually, I came to the conclusion that the following combination of changes would create a superior concept:

1) Cars on a guideway.

A car guided by a monorail is much safer that a car guided by the friction between tires and a road surface. Very early in the RUF development I was sure that a triangular monorail would be the best because it not only is safe, it also feels safe to "ride" on top of the triangular rail.

2) Electric cars powered from the guideway.

Electric cars are very attractive, but in normal traffic you don’t get many benefits since you are still caught in the same traffic jams. Having access to a guideway means that you can recharge batteries, so your range limitation is eliminated. You also get a short and predictable travel time.

3) Coupling of vehicles in "trains".

In order to maximize capacity and minimize air resistance, platooning is an important part of the concept. It only makes sense if there is a reasonable distance between the access points of the network. At least 3 km (2 miles) should be used, but 5 km is supposed to be optimum. Using electric motors make it very easy to control the platooning since their torque characteristic is smooth unlike a gasoline engine.

4) Implementation via Public Transport.

The first system is always the difficult one. Who will buy a vehicle without knowing if there will ever be a guideway for it? Who will create a guideway without knowing if people will buy the vehicles and use it? This dilemma can be solved by introducing the RUF system as a Dual Mode Public Transport system in the beginning. It is possible with Dual Mode to create a very attractive system based upon small electric busses (maxi-ruf) using the guideway as an automated train and using the roads as a Dial-a-Bus collector. The passengers experience a big improvement when they can stay seated in the same vehicle from start to stop. Door-to-door public transport is possible with Dual Mode.

Many more details can be listed. Please refer to www.ruf.dk for further details.


With Dual Mode it is possible to improve transportation significantly, both in terms of travel time reductions, energy consumption reductions and safety improvements. The vehicles can be very attractive in design and IT integration can add some new features making Dual Mode vehicles more attractive than normal cars.


Last modified: July 12, 2001