# The Effect of Speed Humps on Instantaneous Traffic Emissions
## 2 Related Work
### Traffic-Calming and Emissions  
Generally, drivers accelerate after a change from red to green in a traffic light, after passing a bump or when there is free space ahead on the road. Conversely, drivers decelerate to avoid collisions with other vehicles, to stop at traffic lights, to reduce their speed at speed limit areas, and to negotiate speed bumps and pedestrian crossings. Unfortunately, these changes in speeds due to acceleration and deceleration, are the main sources of vehicles emissions [8; 9; 17; 18; 19; 26]. Also, in congested traffic, higher emissions are produced at low speeds [1; 2; 27; 28]. Many studies have investigated the generation of pollutants from traffic. Some of them monitor pollutants levels at different control sites on roads [9; 18; 19; 29] and others use specialized equipment mounted on cars to collect information about the traffic flow or the pollutants levels [1; 2; 20; 23]. The data collected from the monitoring of traffic flow, origin and destination of journeys, elapsed monitoring time, length of the roads, traffic composition and weather are feed into traffic simulators to generate acceleration profiles of vehicles that are used by emission estimation software to compute traffic emissions [30; 31; 32]. A similar approach is used to study the impact of traffic-calming strategies on traffic emissions. The monitoring equipment is mounted near the physical location of the speed humps, or the equipped vehicles follow trajectories where there is a speed hump. [PERSON] et al. [20] monitored an increase of about 90% for CO\({}_{2}\), 117% for CO, 195% for NO\({}_{x}\), and 148% for Total HydroCarbon THC. They used an equipped vehicle on a driving cycle of 2.2 km with 14 speed cushions; each at about 140 m distance. [PERSON] et al. [23] evaluated the effectiveness and emissions of traffic-calming measures in a residential area in Korea. The residential area and the journeys were simulated into PTV VISSIM [30] and the results were feed into The Motor Vehicle Emissions Simulator MOVES [31] to compute the emissions for CO\({}_{2}\) and PM. Only one and two speed humps were considered at the simulations. [PERSON] and [PERSON] [19] performed simulations of the impact of traffic-calming measurements in NO\({}_{2}\) and NO\({}_{x}\) emissions in an urban area in Montreal, Canada. The chosen road is about 500 m in length and 17 m in width, the simulation of vehicles journeys was performed with PTV VISSIM, the emission software MOVES, and the Danish Operational Street Pollution Model (OSPM) [33]. They found an increment from 5% to 160% for NO\({}_{x}\) emissions, and from 0.1% to 10% for NO\({}_{2}\) emissions when compared with a high traffic volume base case. [PERSON] et al. [9] studied the effect of speed bumps on air pollution by PM, they used specialized equipment near the traffic-calming devices at ten residential sites in Lithuania, they found a large concentration of PM at speed bumps sites, significantly higher than limit values in ambient air. In the same work, the authors recommend avoiding the installation of speed bumps or raised pedestrian crossings near sensitive buildings such as schools due to the increased generation of PM. [PERSON] and [PERSON] [18] studied the impact of speed bumps and humps on emissions of CO\({}_{2}\) and NO\({}_{x}\). They measured emissions with mobile laboratory equipment at five locations with speed humps installed in pedestrian crossings to reduce vehicle's speed. Speed humps with trapezoidal shape are frequently found at pedestrian crossings, meanwhile speed bumps have semi-circular shape and are more abrupt than speed humps [24; 34].