The space issue of every means of transport varies according to a series of factors, density being the most important. Moreover, every transport mode has unique performance and space consumption characteristics.
The most relevant example is the automotive vehicle. It needs space for mobility (roads), but at the same time, it spends 98% of its existence in a parking space. Consequently, a significant quantity of urban space has to be allocated for hosting cars, especially when they are parked and their economic and social uti-lity is null. The space necessary to a standing car varies from around 10 m2, if the car is parked on one of the traffic lanes of the road, and 25 m 2, in a special parking lot, or even 14 square m in an individual garage, plus an almost equivalent access area.
As for the space occupied in traffic by automotive vehicles, for the traffic of a car in an area with a maximum speed of 30 km/h, , the road has to have 3 m in width and for speeds of 70 km/h, the necessary width of the road is 3.5m. If we consider that, for speeds exceeding 50 km/h, it is necessary to carry out different works for protecting the citizens by the risk generated for high-speed traffic, then we will see that the width of the road reservation is much broader than that necessary for a traffic lane (for example, for the traffic at high speed of a 2 m-wide vehicle, the road reservation can reach 9 m). The traffic of a vehicle on a route at similar speeds does not require such a space consumption.
The other dimension which conditions the size of the dynamics space corresponding to traffic refers to the space between the vehicles that follow one another on the respective route. It depends on the speed. We can noticed that in the speed area between 20 and 40 km/h, a vehicle consumes around 1.2 m2 • h/km (minimum value!) and at 130 km/h, the space consumption will reach around 4 m2 • h/km.
Many of the transit systems, such as buses and trams, which use public space with vehicles, affect to a certain extent, their efficient traffic. The attempt of easing congestion has led to creating a special traffic lane for buses. Other transport systems, such as conventional railway transport and underground transport, have their own infrastructures and, consequently, their own infrastructure access rights.
Space consumers in transport are also transport terminals and the spaces dedicated to transport services. The quantity of space dedicated to facilities such as ports, airports, transit stations, end stations and distribution centres has increased due to the urban population growth and implicitly to freight traffic.
The railway system has a complex structure that, apart from the rolling track, includes many component elements such as the spaces for the general organisation of exploitation and traffic, construction and installation projects, sections for the maintenance of stations, lines and installations, sections for the revision of cars, depots, general and capital overhaul sections for rolling stock. Without these components, the corresponding technical state of the means of transport and thus the safety and continuity of transport services cannot be ensured.
Due to an appropriate land coverage, road transport disposes of a total mobility, while the mobility of railway and inland waterway transport is limited. Significant differences occur between the different technical transport systems from the point of view of transport capacity. If we compare road with rail transport, an automotive trailer can carry between 20 and 40 tonnes, compared to one wagon which can carry between 50 and 80 tonnes, according to the number of axles and the axle load. Although the comparison between the unitary capacities of the means of the different systems provides a first important orientation, it should be considered that in some technical transport systems, exploitation is not made in simple units, but in sets of wagons. Here we can also notice the superiority of the railways which can carry 2,000-3,000 tonnes or even more, depending on the infrastructure capacity. The railways can only be overrun by a set of flatboats which can carry up to 10,000-20,000 tonnes.
As regards passenger transport, if a simple bus for urban and suburban transport has a capacity of 60 – 100 seats, a modular tram can carry up to 300 passengers, while an underground train between 2,000 and 3,000 passengers. In interurban transport, a passenger train with 10 coaches can carry up to 600/1,800 passengers on seats.
All the above examples prove a significant space saving for railway transports, compared to other land transport modes. Therefore, railway transport can carry large freight volumes and a high number of passengers while using less space for the traffic of railway vehicles, compared to the same freight volumes and the same number of passengers carried by other transport modes. At the same time, the costs per tonne-km and energy consumption per tonne-km are 5 times higher for road transport compared to railways.
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