Environmental assessment of low speed policies for motor vehicles mobility in city centers

In order to assess the influence of reducing the speed limit from 50 km h-1 to 30 km h-1 in one-lane
streets in local residential areas in large cities, real traffic tests for pollutant emissions and fuel
consumption have been carried out in Madrid city centre. Emission concentration and car activity
were simultaneously measured by a Portable Emissions Measurement System. Real life tests
carried out at different times and on different days were performed with a turbo-diesel engine light
vehicle equipped with an oxidizer catalyst and using different driving styles with a previously trained
driver.
The results show that by reducing the speed limit from 50 km h-1 to 30 km h-1, using a normal driving
style, the time taken for a given trip does not increase, but fuel consumption and NOx, CO and PM
emissions are clearly reduced. Therefore, the main conclusion of this work is that reducing the
speed limit in some narrow streets in residential and commercial areas or in a city not only increases
pedestrian safety, but also contributes to reducing the environmental impact of motor vehicles and
reducing fuel consumption. In addition, there is also a reduction in the greenhouse gas emissions
resulting from the combustion of the fuel.