; ELSEVIER The Science of the Total Environment 189/190 (1996) 119-124 the science of the WalEllvhMmt IrkybdlryII*Y L*-md.-Ih Impact of the Madrid M-40 ring road on emission from road traffic And&s Monzon*, Javier Villanueva Transport Department, Universidad PolitPcnica de Madrid, E.T.S.I. Caminos, Canales y Puertos, Ciudad Universitarias s/n 28040 Madrid, Spain Abstract Madrid is a city with a high population density and 4.6 million inhabitants. The structure of the city and its location at the hub of the Spanish road network means it has high traffic densities which have a negative effect on the environment. The atmosphericpollution is particularly seriousas a result of the difficulty of dispersing the pollutants owing to long periods of atmospheric stability, inversion, etc. One strategy to improve the situation has beento build orbital motorwaysto reduce the traffic pressure in the mostdensely populated central zonesand to stop heavy traffic passing through the center. In view of the opposition of certain collectives to the completion of the northern section of the M-40 Ring Road, an environmental impact study was made on the distribution of global emissions with and without its construction. After designing models for the traffic behaviour under the two scenarios for 1995, traffic speed and density loadswere obtainedfor eachstretchof the network. Based on the results, pollutant emission was determined for each zone involved. The resultsshow that the new infrastructure will improve traffic conditions, providing significantreductions in journey timesand will alsoreducethe global emission of pollutants in the short term. Keywords: Pollution; Traffic; Regional impact 1. Madrid structure and mobility patterns Madrid metropolitan city has 4.6 million inhab- itants living in high density population areas with an old road structure and extensive mobility pat- terns. Madrid city is the core of the Madrid Region which is located in the center of Spain * Corresponding author. Tel.: + 34 1 3366658; fax: + 34 1 3365552; e-mail: tr05@dumbo.caminos.upm.es (Fig. 1). This produces substantial problems of congestion and negative effects on the environ- ment in terms of pollution and noise. The situa- tion is particularly serious in view of the high percentage of heavy vehicles involved as a result of goods deliveries inside the city, the communica- tion between the industrial areas on the outskirts and the substantial volume of through traffic which is generated [l] since Madrid forms the central hub of the star-shaped network of Spanish highways. Fig. 2 shows the different zones in the 0048-9697/96/$15.00 0 1996 Elsevier Science B.V. All rights reserved PII SOO48-9697(96)05199-S