In this paper some results relative to tests performed on road with a Fiat Panda Bipower, (CNG and gasoline powered), and a New Panda Twin Air with auto Start & Stop system, are presented. Gaseous emissions are measured with Portable Emission Measurement Systems (PEMS) on two different urban routes, in terms of traffic and slope characteristics during in use experiments. PEMS testing offers an easy and efficient way to evaluate the vehicle emissions over a huge variety of conditions and provides us a direct way to study the in-use emissions of combustion engines, when you want to verify the effect of the traffic and of a particular device on fuel economy and emissions reduction. Moreover now PEMS performances are very comparable to those obtained by standard laboratory instrumentation systems. Instrumentation installed on board for the measurement of gaseous emissions is a Semtech analyzer coupled with an exhaust flow meter; also vehicle position is individuated (from GPS) and engine parameters (via ECU or CAN) are registered at 1Hz.The aims of this activity are to compare fuel consumptions and emissions on road during real world experimental tests, in order to identify and characterize representative road routes. The tests were carried out on different routes of the city of Naples: Route A, an area mostly plane, and Route B, in which orography changes suddenly in slope. Each trip realized by vehicles is subdivided in kinematic sequences and the vehicle emissions and fuel consumption are analyzed and presented as value on each kinematic sequence. The kinematic sequence is the part of motion of the vehicle between two successive stops. Having to take into account the evolution of the vehicle operating conditions, a sequence must be characterized by a number of variables. So statistical methods are necessary to interpret and to correlate emission and fuel consumption results. In the first phase tests with the Twin Air were driven by switching off the Start & Stop system. Then the tests with this car were repeated on the same routes (A forward / back and B) activating the Start & Stop. So the objective is to compare the measurements made with and without the start-stop functionality and on the two paths. Moreover, the results are also compared with those obtained by the other car Fiat Panda Bipower, (gasoline powered) on the two routes.Different types of comparison of vehicle emissions and fuel economy in different driving conditions and with or without a specific device, allows us to better have insight into the variability of emission behavior of a vehicle in real use.