![]() “Biomass makes up fifty per cent of the renewables mix in the E.U.,” Rita Frost, a campaigner for the Dogwood Alliance, a nonprofit organization based in Asheville, North Carolina, told me. Across much of Europe, countries and utilities are meeting their carbon-reduction targets by importing wood pellets from the southeastern United States and burning them in place of coal: giant ships keep up a steady flow of wood across the Atlantic. So it may surprise you to learn that, at the moment, the main way in which the world employs trees to fight climate change is by cutting them down and burning them. ![]() Someone tweeted, “This should be like the ice bucket challenge thing.” Earlier this year, when a Swiss study announced that planting 1.2 trillion trees might cancel out a decade’s worth of carbon emissions, people swooned (at least on Twitter). And last month, when Ethiopian officials announced that twenty-three million of their citizens had planted three hundred and fifty million trees in a single day, the swooning intensified. The results can also be beneficial for other countries within the region.Of all the solutions to climate change, ones that involve trees make people the happiest. US EPA MOVES was calibrated to Qatar conditions which can be used to estimate emission factors and quantify vehicular emissions along other corridors in the country. Intersection geometries along with the control type have significant impact on emission rates and play a major role in assessing environmental impacts. Implications: A microscopic simulation approach using VISSIM and MOVES was developed to assess the environmental effect of converting four three-lane roundabouts to signalized intersections along a heavily congested urban corridor in Doha, Qatar. Both recorded nearly the same emission rate. The results also revealed that there was no significant difference between emission rates in the vicinity of the two types of control. Immediate roundabout upstream approaches are driver behavior dependent, characterized by substantial coasting at lower speeds and subsequent re-accelerating with less idling, described as acceleration events, which resulted in high emission rates, while signalized corridors are signal timing dependent, characterized by ample idling with less coasting and re-acceleration, resulting in reduced emission rates. A more detailed analysis revealed that roundabout corridor operations' effects on emission rates are divergent from those of signalized corridors, particularly upstream and downstream of the intersections. Preliminary results indicated that the signal control outperformed the roundabout in the range of 37% to 43% reduction in emissions. A decision was made to switch all roundabouts to traffic signals for better operations. In this study, a microscopic simulation approach using VISSIM and MOVES was developed to assess the environmental effect of converting four three-lane roundabouts to signalized intersections along a heavily congested urban corridor in Qatar. However, there are other important factors that affect major arterials operational characteristics, factors that are not fully addressed, such as the impact of emissions. Different predefined procedures are available to calculate some of the main operational characteristics, such as capacity, delay, and level of service, in order to select the best type of control. The type of control at intersections has a major effect on the operation of any urban corridor.
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