![]() ![]() Indeed, in most cases, their carbon storage capability easily outweighs their methane emissions. Nobody is arguing that trees are therefore bad for climate and should be cut down. It now seems that most of the world’s estimated 3 trillion trees emit methane at least some of the time. And she had discovered a hitherto ignored major source of the second most important greenhouse gas in the atmosphere. Her 2014 expedition plugged a gaping hole in the planet’s methane budget. ![]() She found that trees, especially in the extensive flooded forests, were stimulating methane production in the waterlogged soils and mainlining it into the atmosphere. Then Sunitha Pangala, a British post-doc researcher, spent two months traveling the Amazon’s waterways strapping gas-measuring equipment to thousands of trees. Around 20 million tons was simply unaccounted for. Until recently, one of the most troubling was the vast methane emissions emerging from the rainforest that were observed by satellites but that nobody could find on the ground. The results can also be beneficial for other countries within the region.There are many mysteries in the Amazon. 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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