Also feeding from the road has been tested many times but has so far been abandoned for several reasons. The most important reasons are shown below:
- Personal safety
- Objects on the road such as stones and sand
- Rain, snow and ice
The most important of the issues raised with regard to direct feeding from the road is the safety of people and animals on the road.
To have an exposed and energized conductor outside a fenced area requires special solutions. But we can compare with sockets in the walls. Here one can get an electric shock if one puts a metal object into the sockets. This is, however, well known and accepted and it happens very seldom.
Elways solution to the safety issue can be summarized as:
- The conductor is located in a trench below the surface of the road and cannot be touched by just walking on it. It takes that you put a thin finger of an object into the trench to make contact with the conductor.
- Only short parts of the trench are energized at any one time, only when a vehicle passes that stretch of road. If someone should put two fingers into the track he/she might get an electric shock but he/she will sure be run over by the vehicle that has initiated the energizing some seconds later.
- If a vehicle should stop the electricity will not be turned on. This is because the velocity is calculated and below a lower velocity limit the electricity is not turned on.
- All systems can fail so the switches are supervised. Should there be voltage travelling along the trench without cars passing, the whole section will be taken out by a breaker switch.
- All electrified roads will have signs stating that they are electrified and that one should not put fingers or objects into the rail.
- The media should also be utilised to inform what electrified roads are and how to behave when travelling on them.
Obstacles on the road
Bigger obstacles can be discovered by radar of the same kind as are used today to discover animals and people on the road. At discovery of an object the contact arm is lifted up in order to avoid damage to it.
Smaller obstacles can be handled by a special design of the contact that makes it survive a collision with smaller stones and other small objects. This has been tested in full speed and the solution works satisfactorily.
One problem is that rain water will enter into the track. At peak traffic and not too intense rain this is not a big problem as the contacts are designed to trough the water out of the track. At roads with an average traffic intensity of 5,000 vehicles per 24 hours each track is passed by almost two cars per minute. With a rain intensity of one millimeter per hour (a normal intensity in Sweden) the track will be filled with around 100 mm per hour. But during that hour more than one hundred vehicles have passed and thereby emptied almost all the water.
When it is snowing a similar situation is at hand. The cars will keep the track free from snow as long as the traffic intensity is of a certain level. At very heavy snow the road it will need ploughing and it is foreseen that the snowplough car will have a special device that can also clean the track from snow. One of the devices we have patented will eliminate this concern.
At low temperature ice can form on the road. This is normally no problem as long as the traffic is dense. However, at low traffic intensity in the night ice could form on the conductors and this ice could isolate the conductor from the contact. In order to prevent this track will be equipped with electrical heating that can be used during exceptional conditions. This will only be necessary in countries where the temperatures regularly reach freezing.