Background Fine-dust or particulate matter are able to penetrate deep into the lungs, triggering not only respiratory diseases but also damaging the cardiovascular system. Children and elderly people are particularly vulnerable. Fine dust pollution is caused primarily by local road traffic, more specifically combustion-related diesel exhaust emissions on the one hand and re-suspension of road dust through abrasion of the road surface on the other. Pollution is therefore worst in towns and cities. Many European cities, including the project city Klagenfurt, exceed the dust pollution limit recommended in the Air Quality Directive (1999/39/EC) on more than 35 days during the coldest six months of the year. The limit for particulate matter (PM10) is 50µg/m³. A previous LIFE project (LIFE04 ENV/AT/000006) found that almost 25% of PM10 pollution is due to re-suspension on busy roads. Urban populations are also affected by traffic and roads in the form of noise pollution. An OECD study has indicated that some 50% of the 826 million people living in OECD countries are exposed to traffic noise of over 55 dB and some 16% of the noise generated by traffic is over 65 dB. Objectives The SPAS project aimed to tackle the problem of re-suspended particulate matter from road surfaces in urban areas. It sought to demonstrate an innovative technology for eliminating the particles at source - a particulate-matter filter along the side of busy roads and in tunnels. It furthermore planned to combine the filter with a sound barrier, to simultaneously reduce noise and dust pollution. It targeted a clearly measurable reduction of pollution with regard to both particulate matter and noise from a busy road. The project expected to test and optimise the Sound and Particle Absorbing System - SPAS - for various types of roads and fields of application. Results The LIFE project SPAS successfully developed and tested an innovative combined noise and fine-dust filter for roadsides. This unique system was able to reduce fine-dust particles produced by re-suspension at origin by approximately 15-30%. It reduced noise by up to 7dB. The project team tested and optimised fine-dust filters in laboratory. They identified the best material to provide low filter resistance and high absorption capacity whilst being recyclable at end of use. A project partner used computer models to calculate the optimum position and alignment of the trial walls so that passing traffic ensured good air flow through the filters. The project used a test bed in a tunnel to assess the performance of more than 20 different filter types. They particularly measured fine-dust absorption rates and pressure loss across the filters. Ultimately, two different preferred options emerged: a two-stage filter consisting of a coarse filter and a fine filter for roadsides; and a single-stage, fire-resistant version for tunnels. The individual filter elements themselves consist of a riveted aluminium frame, into which the filter media are inserted. They can be easily removed for maintenance if they suffer visible damage and at end-of-life. However, a cost-benefit analysis of regenerating the filters found that it was economically inefficient to clean the filters for re-use. The project installed three trial walls totalling 564 m in Klagenfurt: a totally new roadside filter; a new filter system retrofitted to an existing noise-protection wall and, the installation of filters on a tunnel roof and sidewalls. The team measured levels of PM10 and nitrogen oxide (NOX) at the test sites. They also recorded meteorological parameters, traffic data, noise levels behind the walls and filter-maintenance measurements. The SPAS filters reduced PM10 by about 15-31% alongside the roads and by 23% in the tunnel. Further investigations have shown that re-suspension of PM10 accounts for about 75-80% of the entire road-related fine dust burden in tunnels and on rural roads. This increases the overall importance of reducing this form of pollution. At one site, noise levels behind the new integrated filter wall dropped by about 7dB, which is equivalent to a 80% decrease in traffic and brought roadside houses and gardens within accepted noise pollution limits. The retrofitted wall - which was raised in height by about 0.5 m - reduced noise by 2.1dB at ground-floor level. Positive results were also achieved at the tunnel site. The SPAS project demonstrated the benefits of both new and retro-fitted combined noise and fine-dust filters. Due to the development and the production of the new technology 3 job positions were created during the project duration. Possible further positive socio-economic effects are depending on the future demand of the SPAS elements. To raise awareness of this innovative and easily replicated technology, the project produced a range of printed materials, a website, information events, on-site visits and an important closing congress with more than 300 participants from 17 countries. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).