An evaluation of the LPG vehicles program in the metropolitan area of Mexico City

The environmental agency in the metropolitan area of Mexico City has launch ed a program to introduce more energy-efficient modes of transport, one of which is the use of alternative and less polluting fuels. With that perspec tive in mind, a liquefied petroleum gas (LPG) fleet of vehicles is exempt o f the mandatory "one day without a car" program if the emission of pollutan ts is below the standard authorized for that specific purpose. Today, about 28,000 light-duty vehicles and heavy-duty trucks circulate in the area, mo st of them as aftermarket converted vehicles. In this work, we evaluated re gulated exhaust emission and other parameters on 134 representative vehicle s of that fleet. From the data obtained, an estimate of emission factors an d their contribution to the global emission in the metropolitan area is pro vided. It is concluded that more than 95% of the in-use vehicles using LPG presented regulated emissions which exceeded in one or more the environment al regulations values required for certification. The poor maintenance of t he vehicles and the type of conversion kit installed could be the culprits of the results obtained.