NOx and NO2 Benefits of Advanced SCR Systems

All buses were tested over the bus Route 7 through the city of Brighton & Hove which is an important central corridor for public transport in the east and west directions and has the characteristics of inclination, traffic congestion and road junctions where road-side air quality measurements show elevated levels of NOx and NO2. The outward journey is about 9 km and contains both uphill and downhill driving, but is net downhill. The return journey follows a highly similar 9 km route and is net uphill. The route altitude varies from sea-level up to 60 m with several sharp inclines and declines, operation on flat terrain is minimal, Figure 2. Open image in new window FIGURE 2 Route 7 — Altitude versus distance on route outbound (to Marina) and inbound (to depot) journeys (© Ricardo) The busses were driven around the route in a manner that was considered to be representative of normal service, including specified dwell times at each bus stop and a fixed break period between the outbound journey and the return. Each bus drove Route 7 three times with the same driver and the Euro IV bus was driven on two further runs, each by an additional driver with a different characteristic style. In order to replicate the true duty cycle, all buses were loaded with ballast equal to 70 % of the maximum passenger loading. For safety reasons the truck undertook a slightly modified route to avoid tight corners, and made fewer halts. Truck tests were conducted with an empty trailer and with a trailer loaded with 20 t of concrete ballast. Data were continuously acquired and careful extraction of the data permitted the emissions within specific geographic zones to be evaluated within the resolution of the GPS, against traffic control measures, the air quality monitoring stations and bus stops. In agreement with the Brighton & Hove Bus and Coach Company, it was analysed the emissions profiles from Route 7 in both directions and in particular from North Street which is a congested 420 m road restricted to buses, taxis and occasional delivery truck. It is in the centre of Brighton, frequented by many pedestrians, with an average slope of 3 % and an air quality monitoring station situated close to the roadside.