Atmospheric Environment 40 (2006) 4547–4561 Emission control options for power two wheelers in Europe Leonidas Ntziachristos a , Athanasios Mamakos a , Zissis Samaras a,Ã , Anastasios Xanthopoulos b , Eleftherios Iakovou b a Laboratory of Applied Thermodynamics, Mechanical Engineering Department, Aristotle University Thessaloniki, P.O. Box 458, GR-54124 Thessaloniki, Greece b Laboratory of Quantitative Analysis, Logistics and Supply Chain Management, Mechanical Engineering Department, Aristotle University Thessaloniki, P.O. Box 458, GR-54124 Thessaloniki, Greece Received 23 December 2005; received in revised form 2 April 2006; accepted 4 April 2006 Abstract This paper quantifies the emission contribution of motorcycles and mopeds in Europe, in the period 1999–2012. Projections show that these vehicles will emit more than 7% and 20% of total road transport CO and HC, respectively, by the year 2012, if no additional regulatory measures are taken. In contrast, they will continue to be negligible NO x (0.7%) and CO 2 (o1%) emitters, while their particulate matter (PM) emission contribution is expected to decline to below 1% in the future. The relative importance of their emissions, however, increases in urban environments, especially in southern European countries, which host large fleets of small two wheelers. Hence, further regulatory measures are being considered which include durability requirements for the emission controls, in-use compliance and roadworthiness procedures, on- board diagnostics, control of evaporation emissions, PM specific measures and new steps for emission standards. The study quantifies the environmental benefits and the costs associated with each measure, and calculates cost-effectiveness figures which may be used to evaluate each policy option. Results show that for the reduction of HC emissions, both evaporation control and roadworthiness tests are cost-effective while a further tightening of the emission standards for mopeds will bring the largest benefit. Additionally, on-board diagnosis for motorcycles is found to be an expensive measure with questionable effectiveness, while the replacement of mineral with synthetic lubricants would bring clear benefits with respect to PM of 2-stroke engines. r 2006 Elsevier Ltd. All rights reserved. Keywords: Motorcycle; Moped; Emission standard; Cost-effectiveness; Emission projection 1. Introduction Mopeds and motorcycles, collectively referred to as power two wheelers (PTWs), are popular means of transportation, particularly in Southern Europe where good weather conditions facilitate their year- round use. It is estimated that in Rome alone, some 150 000 motorcycles and 500 000 mopeds are in operation (De Lauretis, 2005). Because of their small size and agility, PTWs help in alleviating traffic congestion and reduce the energy consump- tion for the transportation of one or two passengers, compared to passenger cars. However, while PTWs are an essential element in improving urban ARTICLE IN PRESS www.elsevier.com/locate/atmosenv 1352-2310/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2006.04.003 Ã Corresponding author. Tel: +30 23 10 996014; fax: +30 23 10 996019. E-mail address: zisis@auth.gr (Z. Samaras).