Buses operating on compressed natural gas

Basic Information


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New buses running on compressed natural gas (CNG) have been integrated in the urban public transport fleet, reducing emissions of pollutants and cutting smell, vibrations and noise.

Implementing sustainable mobility

According to data obtained through trials of different vehicles, using CNG rather than diesel can achieve a reduction in pollutant emissions (nitrogen oxides, carbon monoxide, hydrocarbons and solid particulate matter) of between 82 and 98 percent for each 100 kilometres travelled. However, the energy consumption of CNG buses is 46 percent higher than that of the standard diesel alternative. In addition to the reduction in emissions of exhaust gases, reductions in smell, vibrations and noise (both internal and external) have been recorded in surveys of bus passengers and drivers, indicating improved satisfaction following the introduction of the new service.

The city’s transport operator, Transports Metropolitans de Barcelona (TMB) first started trials with two CNG buses in 1995, and the results confirmed the reduction in emissions of pollution and noise from these vehicles compared to vehicles operating on diesel oil. In 2000, TMB signed an agreement with the energy company GAS NATURAL to introduce CNG as an operational fuel for the bus fleet. Between 2001 and 2002, a fleet of 70 CNG vehicles was put into operation. These are standard 12-metre buses supplied by IVECO and MAN.

One element of the measure was the evaluation of the buses’ environmental and energy performance under real operating conditions, while the other was the installation of equipment and the adaptation of one of the city’s biggest bus depots (Zona Franca I) for the maintenance of CNG vehicles. As a result of the measure, TMB became the pioneer CNG bus operator in Spain, and one of the first in Europe to obtain ISO 14.001 environmental certification.


In order to carry out the feasibility studies, the vehicles were put into operation on different types of lines and a comparative analysis of performance was undertaken. The selected lines were services 22, 57 and 157. The first is a hilly route with considerable changes in gradient, while the others are flat routes. The trials were started in parallel with the first phase of the installation of equipment and infrastructure relating to gas supply, storage and distribution. The conclusion was that on lines with significant changes in gradient the performance of CNG buses was worse, thus the new vehicles are normally assigned to lines running on flat routes.

Gas is supplied by pipeline directly to the TMB’s refuelling station located next to the Port of Barcelona, in the Zona Franca industrial estate. The Zona Franca I bus depot is equipped with all the necessary technology, allowing for the refuelling of CNG vehicles in less than three minutes.


The new engines, and the CNG-related elements, such as gas tanks, incorporated many technological improvements compared to the earlier bus fleet. The introduction of CNG vehicles was extremely successful, due to the good performance of these buses and to their positive acceptance by users.

This fact sheet has been updated by a third party on the basis of available information (not by the city itself), therefore we do not guarantee any data with respect to their content, completeness or up-to-dateness.


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