Once we identify this source of dangerous behaviour we must ban it whether it is pedestrians crossing highways or perhaps other vehicles. In fact I propose that we take a look at our accident data to find out the sources for the incredible carnage on our roads today. I agree that as planners we must ban all behaviour which could possibly be dangerous. The bad news is that so many planners use them as their prinicipal guide. The good news is that many FHWA specifications are either flexible or merely suggestions. We have a RR overpass where ped's cross 2 sets of high speed tracks at-grade because our pedestrian bridge takes too long to climb. If it takes too long to go over an overpass, people will opt to cross at-grade which can be dangerous. From my experience, overpasses are generally more intimdating for people to climb/bike who are not in good physical condition. Keep this in mind that before considering pedestrian perception. The last factor you may want to consider is displacement of homes, typically overpasses takes more RW and houses due to embankment, whereas pilings can be driven and minimal RW is required for underpasses.Ĭonsider housing (displacing homeowners), soil types, drainage, maintenance and your budget allowance when choosing an overpass over an underpass. Overpasses typically need plowed more often (cause they freeze first being exposed to the elements).Īnother constraint could be drainage, if you are near the water table, many pumps and piping are required for underpasses. Maintenance (especially in snowy regions) plays a big role also. In our city, bedrock is 3-6' deep throughout town and makes underpasses cost prohibitive, with the need to dynamite rock and excavation. If you are overpassing RR tracks, that would be the way to go, since the RR would have to spend money to re-route their tracks which could be VERY expensive.Īlso your soil type could be constrictive. If you are overpassing water it may be scenic. Toledo, OH had an overpass where some kids dropped a steel plate off of it and it killed a driver. If you are attempting to overpass another road, you may want to consider vandals dropping items off the overpass onto cars below. I would also add that it would depend on what you are overpassing/underpassing. For the most part, they are the national authority for most guidlines and studies related to traffic. Pedestrian Safety Guide and Countermeasure Selection System 4-79Ĥ.16.4 Separation on Combined Structures.4-81
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