TMB’s strategy for an efficient bus network in Barcelona

Like most big European cities, Barcelona has severe problems with air pollution due to several factors, like industry and domestic emissions, but especially due to road transport emissions. In the Metropolitan Region of Barcelona, transport contribution to energy consumption accounts for 40%. TMB is the main public transport operator for the metropolitan area of Barcelona and an international reference in the urban transport sector. TMB accounts for almost 80% of such transport and the services provided are essential for the two million journeys made by passengers every working day – some 577 million per year.

To carry this amount of people every day, the metro network is formed by eight lines and the funicular railway, and has 140 stations distributed along 102.6km while the Barcelona bus fleet comprises 1,090 units, with energy consumption equivalent to 27 million litres of diesel fuel per year.

Achieving a clean and energy-efficient public transport is one of the most important objectives of the city. For this reason, the City Council and TMB are working to introduce new transport models that help improve the quality of service, are more efficient and, at the same time, contribute to more sustainable developm – ent in Barcelona and the metropolitan area.

During the last decade, the main focus of improvement of the bus fleet has been the local environment, in order to comply with the European Directive on Air Quality.

Successively, several traction alternatives have been used on the buses.

In 2001, TMB started a development of a CNG bus fleet, equipped with 3-way exhaust catalysts, to reduce the NOx and PM emissions by more than 90%. This policy has shown large emission reductions and today Barcelona has 376 CNG vehicles (35% of the fleet). An agreement between TMB and Gas Natural Fenosa anticipated an increase in the CNG fleet by 124 buses before 2015. In 2015, the total number will be 500 units – almost half of the total.

During the period 2003-2006, TMB participated in the Mercedes CUTE Project, operating three hydrogen fuel-cell buses to demonstrate the viability of the technology. The results were quite satisfactory, but the cost was too high, showing that technology needed to mature.

In 2006, TMB started trial tests with biodiesel, which offers a global reduction of CO2 emissions of almost 80% against the use of normal diesel fuel. Today a complete depot with 125 buses is run with this fuel (12% of the fleet).

But the major problem found during these 10 years has been that every new technology used to reduce exhaust emissions has generated an increase in fuel or energy consumption. Therefore, to achieve a new energy-efficient bus network and meet targets for improving quality of life of citizens and mitigating climate change, a global project is required. The summary of this Environmental Sustainability Master Plan is the deployment of a new bus network and implement the first step, a BRT (Bus Rapid Transit) system, operated with the help of coordinated traffic lights to give priority to buses and their new associated infrastructures, and with progressive introduction in the bus fleet of new traction technologies to improve its global energy efficiency, plus the additional efficiency achieved at bus garages.

Dedicated lanes, priority at traffic lights and adapted vehicles

An important part of this global project is the RetBus network proposal, a new type of surface public transport for Barcelona. The City Council and TMB are developing the first level of this BRT-type system or a bus with a high level of service which provides surface transport with similar features to the light-rail, exceeding the limitations of conventional buses and attractive enough to appeal to new users.

The studies made by the City Council, TMB, the Centre for Innovation in Transport (CENIT), the Technical University of Catalonia (UPC) and UC Berkeley professor Carlos Daganzo, show that the main benefits of these buses are that they run more often and offer a shorter journey time. To achieve a commercial speed higher than a conventional bus, distance between stops has to be longer and it must travel at a higher running speed, and therefore be given certain priority at intersections.

The RetBus differs from other surface transport systems in its infrastructure (separate bus lane or bus lane with intermittent priority), operation (double stops, macro regulation of traffic lights, dynamic priority) and the vehicles themselves (articulated or bi-articulated units) (image, seat distribution, on-board information screens).

Plans are made to complete the staggered introduction of a system of high-performance buses along 12 transport corridors, seven vertical and five horizontal. Ideally, four corridors will be introduced per year, until all 12 are operative. The restructuring of conventional lines will be completed in the same way. Each corridor has its own detailed study and plan with the necessary infrastructure and operation measures. So far, a detailed study has been completed of the infrastructure necessary for the four corridors in phase one – two vertical and two horizontal.

To achieve this, the City Council is working on the design of new signalling coordination, taking into account the special operation features of the service vehicles (existing commercial stops, commercial speed, etc.). Furthermore, to improve the impact of the previous measure, the Mobility Area is involved in the deployment of next-generation traffic devices to give priority to buses. At the same time, new traffic lights require new capabilities of the intersection controllers.

For their part, TMB have been working, amongst other aspects, on rolling stock and organisational measures to bring these corridors into operation in the near future.

Innovation in air quality improvement

To achieve the sustainability objectives of the mobility plans, TMB is also planning a technological fleet improvement, with a large deployment of an electric & hybrid bus fleet, by purchasing new units or retro-fitting old diesel ones. According to the specific type of vehicle, hybrid technology can offer energy efficiency between 20% and 30%. The objective of the hybridisation Retrofit project is to technologically and environmentally update 80 vehicles from TMB’s bus fleet, in addition to revitalising the Catalan industrial sector in an interesting area of research, development and innovation.

Recently, TMB has acquired four new buses that run with hybrid technology from Castrosua and MAN. However, Barcelona is special in this Retrofit project and not only for buying hybrid vehicles like other cities. TMB prefers to convert current diesel buses to hybrids in order to make them cleaner, quieter and more efficient.

The first step in this regard was the building of a hybrid prototype (diesel-electric) that is currently in circulation, as well as four other hybridised vehicles. These new vehicles are part of the Retrofit programme for the mass conversion of diesel buses to hybrid technology.

Technically, the prototype was built with the series configuration, where the diesel engine, connected to an alternator, produces electricity whenever necessary, without affecting the traction. The energy generated in this manner is stored in high-capacity capacitors (ultracaps). The propulsion itself is carried out by two 67-kW three-phase electric motors. These are connected to the traction, without using a gearbox, which has been eliminated. These same motors act as electricity generators during sudden braking to charge the accumulators.

TMB has combined the experience of the diesel Retrofit project with the support of the Spanish government and the company Gas Natural Fenosa, to build the first retrofit natural gas engine bus to convert into a CNG-electric hybrid vehicle. The prototype has been incorporated provisionally into the TMB fleet and the company will study the benefits in terms of reducing energy consumption and emissions and thus its viability for future use. This new experience is under analysis for mass conversion.

The companies have worked together on developing the prototype, built based on the CNG-propelled bus currently operating in the TMB fleet, in order to verify the technical solutions adopted, emissions reductions and, in particular, the fuel savings achieved with this new model.

To promote the cleanest and most efficient options for the propulsion of the bus fleet, from now on TMB will only buy buses that run on compressed natural gas, hybrid and electric technology.

Under the same agreement, high-efficiency filters are being introduced to trap exhaust pollutants in approximately 500 diesel buses to reduce emissions. So far these filters have been installed in 200 vehicles and will be installed in the entire fleet by the end of 2011. This measure will bring about a reduction of almost 200 tonnes of NOx emissions per year.

The project of a new public transport bus network and the renewal of the fleet of public buses will contribute to the EU 20/20/20 objectives, and to achieving the objectives of energy-efficiency, quality of life for citizens and mitigating climate change.

As a result of these strategic policies to protect the environment, Barcelona has won awards in the second edition of OSMOSE for integrating innovation in the urban transport and mobility sectors. These awards are given every four years by the Association for European Transport. Barcelona has been chosen for its commitment to promoting public transport to reduce the use of private vehicles. Specifically, initiatives such as the RetBus project (the fast bus corridor network), the conversion of diesel vehicles to hybrids (both electric and CNG), and low-consumption traffic lights with LED technology have been recognised.

As evidenced by this Environmental Sustainability Master Plan, protecting the environment is a core issue of TMB’s strategic policy, and will continue its commitment to ecoefficiency, combating pollution and climate change and fostering a culture of sustainability.