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Module 1: Safe and Sustainable Transportation Systems

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Predicting Methods for Conflicts

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Let us look at, uh, the different ways to, uh, uh, predict, uh, uh, vehicle pedestrian and vehicle bicycle context, right? Uh, vehicle to vehicle conflicts, uh, are, uh, dealt with, uh, in different types of fashions, uh, and have been, uh, a major, uh, research area for a long period of time now. Whereas, uh, when it comes to vehicle to pedestrian and vehicle to bicycle, Uh, crashes. It has not. Uh, the research has not that robust yet, especially because these are even, uh, very few of these crashes are reported in the first cases. Uh, and since they are mostly concentrated around low speed roads, uh, in urban areas, it is very difficult to usually predict them. So let us look at how we can do that using your SPF and, uh, accident modification factors, and also, uh, what are some of the common interventions. That are used to improve pedestrian safety in your area. Uh, if you, uh, if you look at, uh, some of the statistics that are coming out, uh, and not only in India, but, uh, everywhere around the world, what you would notice is that, uh, the vulnerable road users, right? The pedestrians and the bicyclists, they constitute a large portion of the, uh, uh, People who are actually getting killed in these accidents, right? Because they have, they are not shielded to the environment. They are exposed to the environment. So any kind of accident that they are involved in, it is usually, uh, that person, uh, either, uh, uh, uh, uh, uh, severe injuries, serious injuries, or are either, or are killed in those accidents. So you'll see that on average, 40% of the total fatalities are. Pedestrian fatalities and, uh, uh, and some statistics in a, in a particular year, uh, this was the highest that was shown, uh, that was seen in Mumbai. So what, uh, how can you, we use these, uh, safety performance functions, our SPS, uh, in the case of, uh, predicting, uh, vehicle pedestrian collisions, but yet, right. So we already know, uh, how the safety performance functions look like and. How accident modification factors have to be multiplied with them in order to, uh, predict the number of, uh, crashes. So similarly here, if you want to predict the number of, uh, pedestrian, uh, pedestrian related crashes, you have to know, uh, the, uh, um, uh, uh, predicted average crash frequency for an individual roadway segment. Right? You have to know that, and then you have to multiply it with. Uh, some sort of, uh, uh, pedestrian adjustment factor, right? Pedestrian accident, adjustment factor. So if you multiply that, so this is already what we have shown you in the previous, uh, previous lecture, uh, NBR or the predictor average, Cassius is nothing, but it is the safety performance function for a particular type of, uh, facility. For base conditions multiplied by different types of, uh, accident modification factors, right? So this takes does not take into account vehicle, uh, vehicle pedestrian or a regular bicycle collision. So this is average. This is normally you are developed for vehicle to vehicle crashes, uh, using the different modification factors. But once you know that, and if you use, uh, that and multiply it with. Uh, uh, what is called a pedestrian accident, adjustment factor, uh, then you can predict the number of, uh, pedestrian to, uh, vehicle crashes. So in order to know, what are the pedestal accident adjustment factors? What is usually seen as the most, uh, important, uh, criteria, uh, is, uh, the different road types and the speed limit, the posted speed limit. There's not the speed at which the vehicles are moving. It is actually the posted speed limit. So it is likely to depend upon also climate and different working environments. But so far, what we have been able to see, uh, through research is that if the, uh, if there are different types of roadways, for example, uh, this is a two lane undivided road, right? To you, meaning two-lane undivided road. Uh, three T meaning it's a three lane road with a center turning lane or something like that. Whereas this is a four lane and divided as a four lane divided, similarly of violin. Uh, so it's with the center lane center turn lane. So the pedestrian frequencies are the pedestrian crashes, crash frequencies vary by these different types of roads and also by different types of, uh, speed, uh, that is posted there. So, uh, uh, factor, uh, if the posted speed limit is 30 miles per hour low, uh, the value of F F pedestrian, right? That is that. Uh, but, uh, what we have seen in the previous slide, which is the pedestrian accident, adjustment factor F PDR, right? But it's an accident, or just in fact, at this 0.036. Whereas if the posted speed limit is greater than 30 miles per hour, it is 0.0, zero. Five. So what that tells you is the discipline factor is much lower. Uh, if the, uh, speed, uh, if, if the speed is higher. So if the adjustment factor is much lower and the speed is higher, meaning, uh, uh, maybe when the posted speed limits are, uh, higher than 30 miles per hour, usually. Uh, the number of pedestrians walking along that type of road is much lower. So the probability of a pedestrian Wakeland passes low, maybe that's what it is indicating towards. Right. Whereas, uh, as soon as you have a street where the posted speed limit is 30 miles per hour lower, uh, that means they are, uh, kind of more pedestrian friendly kind of streets. Then you have to have it at just a greater adjustment factor. So similarly you can see it for different types of roadways. So in case of, uh, uh, trying to predict the number of pedestrian and vehicular crashes, uh, pedestrian, regular crashes, the important thing to know is the type of road and also the posted speed limit. These two factors. I will allow you to understand, uh, the pedestrian accident, uh, discipline factor, which you then multiply with your, uh, uh, normal number of accidents, uh, that are, uh, predicted to happen on that road, uh, using the SPF function SPF, uh, for the base conditions. Uh, then if you multiply those two, we'll be able to predict the number of vehicle penalty crashes. Similarly, in order to, to understand, uh, or predict the number of, uh, Um, a vehicle, a bicycle crashes you have to, uh, multiply the, uh, bicycle adjustment factor F biker with a predicted average crash frequency on any individual roadway segment, excluding all these crashes. Right. Again, it is very similar to, uh, the question that we have seen for. Pedestrians as well. However, in this case as well, uh, for, uh, for, uh, bicycle, uh, for bicycle adjustment factors are also dependent on posted speed limit signs and the different types of, uh, roadways. However, the values are a little bit different, uh, in case of, uh, pedestrians versus in case of, uh, bicyclists. So. That is how you can usually predict the number of, uh, vehicle pedestrian crashes, uh, and vehicle bicycle crashes. So if you have a simple, uh, example where if you were to ask to be, uh, estimating the pedestrian crash frequency and the bicycle crash frequency. For a particular type of facility, which is a two lane undivided arterial with the sport posted speed limit of 30 miles per hour. Uh, having predicted average crash frequency without bicyclists as, without precedent bicyclist as this much. So, uh, if that is the predicted number of accidents without bicycles and pedestrians and the posted speed limit is this what would be the expected, uh, pedestrian crash, frequency and bicycle crash frequency. So you can see that. Uh, from the table, you can use this factor of 0.036. Uh, if you go back to the table, you would see that are posted speed limit of 30 miles per hour lower. And for two lane undivided, the factor is 0.036. So that is the factor that we have used here, uh, 0.036. And that's what you would see that you would are. You would expect that the average crash, average pedestrian crash frequencies. Only 0.2, four, seven classes, but yeah, so that type of facility, you will see very low number of vehicle pedestrian crashes. And, uh, in case of a bicycle, also the value is 0.018, and he will see even fewer bicycle, uh, vehicle crashes. And in that particular facility under a sport, uh, speed limit of 30 miles per hour. Now you can also develop different types of accident modification factors for different types of road segments. For example, uh, these have been developed for if the road segment has on-street parking or not. If there are roadside fixed objects, uh, on that segment or not, depending on what the median wit that is available in that segment, depending upon. What type of lighting is available in that segment. And if there is automated speed enforcement or not on those segments, right? So you remember accident modification factors, uh, depend on, uh, have to be used because SPS are developed for certain types of conditions. Uh, whereas if you want to, uh, implemented for different type of condition, then, uh, you have to use. Uh, or multiply those SPS with these accident modification factors. So different standard, uh, AMS have been developed based on these five different types of, uh, roadway segments. So if you look, uh, at each one of them, uh, one by one, uh, the accident modification factor for, uh, on-street parking says that it depends upon. Uh, whether there is parallel parking or angle parking on your roadway segment. And it also depends upon what type of land use your parking is at. So residential, uh, land use versus commercial or industrial institutional land use, the rates will be different. And also obviously they'll be different for different types of. Uh, uh, different roadway types, right? So these are accident modification factors, and usually they are given, uh, this, uh, uh, uh, equation of this months, which tells you that PPK, which is the proportion of the curve blank with on-street parking, right proportion of goblet, where on-street parking is available. Your segment length may maybe longer, but within that segment length only a certain. Proportion of it, uh, has available or legal parallel parking, uh, parallel or angled parking to it available. And then you have to know that proportion. And if you know, the, uh, total length, uh, that the proportion can be given by just summing up the car blunt, uh, with on-street parking for both sides of the roads combined, usually you combine both sides of the road right up and down a segment, and, you know, the, uh, length of the segment anyways. So if you use that you would get the proportion and then you use the factor, uh, from, uh, from this table, right? Yeah. Uh, to determine what is the accident modification factor that has to be used along with your SPF? Well, on street parking, is that again, this is based on research, uh, by Bahnsen. So all these are evolving research that is happening. All of these factors are being modified, calibrated for different types of. Um, for different types of facilities, but so far everybody, all the research fraternity does agree upon that. Uh, the, uh, accident modification factor for on-street parking depends upon the roadway type, the type of parking as well as the land use that the parking is available at this at least is constant. These factors are something that are being developed for different areas. So, if you were to ask to find the accident modification factor, uh, in parallel on street parking, uh, present along two lane, undivided arterial road in a residential area, and you know that the total car blinked where parallel parking is available is four miles. Whereas your roadway segment is nine miles. Uh, then all you have to do is, uh, calculate the, uh, Uh, calculate the proportion is 0.4, four. You look up, uh, the FPK value, uh, based on, uh, based on, uh, the factor that it is a parallel on-street parking and in a residential area for a two-lane undivided arterial. If you go back to this table, uh, parallel residential, Tulane, and divided. So it is 1.465. So you just use the 1.46, five here and put it in the formula. You would. Have the accident modification factor as 1.204. Now, if you want to bring in, uh, uh, SPF from some other, um, uh, location, or if you want to use an SPF for your particular area, uh, and find out the difference, uh, to the predicted, uh, uh, safety that will happen. If on-street parking, uh, becomes available, then you can now multiply there. The SPF with 1.204. In order to understand what will be the change in the safety of your urban street. Similarly, we will develop a we'll show you, uh, uh, these AMS for, uh, the different types of road segments. The next one is, uh, roadside fixed objects, uh, in this case, uh, the proportion of fixed object collisions, uh, is something that has to be understood. So how many accidents have happened due to. A vehicle crashing into a fixed object, uh, are different types of roads. That is one factor that is, uh, um, uh, that is something, uh, which impacts, uh, the crash rates and also the fixed object offset factor, right? Uh, by how much is the fixed object? Uh, offset by, uh, from the, uh, side of the roads. Right? So again, it can be given by this formula, um, uh, simple formula enough, uh, the offset tractors that are given here, uh, the fixed object density, which is the number of fixed objects per mile on both roads combined is something that, uh, uh, you can find out, you can measure on your street. How many fixed objects, fixed objects, meaning, uh, light balls trees. Um, you know, trash cans, uh, signpost sometimes. So all of those things are fixed objects. You can find out, uh, the density of the fixed objects there, uh, using that. Uh, you can determine the, uh, accident modification factor for roadside fixed objects. Again, this has been adopted from her, uh, research, which was used on predicting you did utility pole. Uh, crashes, right. If there are too many, uh, utility poles, light poles, telephone poles. So what are the, what is the prediction? Uh, how can you predict the number of crashes if there're so many utility poles, uh, similarly by median width, uh, it has been seen that median wit has an effect on, uh, the crash, the average crash frequency. Uh, uh, the effect, uh, although is not very, not very high if you look at it, but still, uh, median wit does play a role. So, uh, if the, if you want to change your median with, uh, from 10 to 50, then you would try, you would expect that there would be some sort of reduction in your, uh, accidents. Okay. Uh, similarly for lighting, if you are, if you're a roadway segment, uh, has. Uh, proper lighting or improper lighting that plays a role in determining the number of crashes that happen on your, uh, on your row, on your street. Uh, again, this, uh, what has been seen by research, uh, of, uh, LV can wise that the proportion of, uh, uh, total, uh, nighttime crashes by severity level, uh, depends upon. Uh, your, uh, lighting that is available. So this case, uh, the factors are developed for fetal and injury and property damage only, right? And also you have to know the proportion of crashes that occur at night, all the prep, all of the crashes, um, uh, was this, how many are happening only at night, you have to know that proportion and you have to, uh, use these factors based on. How many fatal and injury crashes were there versus how many, uh, only property damage crashes, what there to report that, uh, into the equation, you will be able to develop, uh, the AMF for, uh, the case of lighting in your urban street. Uh, this is something, uh, uh, which is, uh, a recent phenomenon where people have. Uh, notice that automatic, uh, automated speeding enforcement, right? Uh, this is, uh, where you are now, uh, getting speeding tickets, uh, are speeding challenge automatically, even if there is no, uh, police on the road. Uh, but there are cameras that are detecting your speed and, uh, sending out, uh, uh, automatic challenge. So the minute, uh, the second, you know, that there is automatic, um, uh, speed enforcement, uh, you usually tend to, uh, And drive carefully. And when you tend to drive carefully, uh, the frequency of crashes also tend to reduce, uh, it has been noticed that automated, uh, uh, uh, AMF for automated speed enforcement is currently taken us 0.95. Uh, then, uh, if you look at, uh, lastly, if you start to look at the different types of interventions, uh, that have been made, uh, for improving pedestrian safety, Uh, you would usually, uh, can group them under five broad categories. One is to reduce the penicillin exposure to regular traffic. Uh, you'll see what that means. The other is to actually reduce the speeds of the vehicles themselves. Uh, finally you have to improve the visibility of the pedestrians, uh, either by, uh, uh, the pedestrians wearing vests are, uh, are wearing a color colored clothing, which is easily visible to the. Uh, vehicles or, uh, through roadway design where, uh, people are actually, pedestrians are actually more visible to the vehicles, uh, or people driving the vehicles, uh, improving the vehicular design for pedestrian protection. So even the, uh, even if the vehicle, uh, pedestrian gets hit by the vehicle because of the design of the vehicle, uh, the, uh, uh, the extent of the injury to the pedestrians, uh, can be lowered and also by providing care today in pedestrian. So. Uh, unfortunately the accident, uh, uh, the crash happens, uh, if you provide, uh, uh, immediate care to the injured person, then the extent of the injury can be, uh, reduced as well. So these are the five broad categories of, uh, interventions that are usually made for improving pedestrian safety, uh, how to, uh, so reducing personnel exposure, usually meaning that, um, uh, at. At specific points along their streets, you have to have, um, uh, facilities designed in such a way that they are either, uh, separating the pedestrians from the regular traffic. Um, either they may be great separated, or they may be, uh, separated horizontally, um, uh, ad grade, uh, uh, from the regular traffic are, uh, they may provide, uh, uh, safe crossings. Uh, at grade, uh, for the pedestrians, uh, but somehow, uh, their exposure to regular traffic or the intermingling of, uh, pedestrians and regular traffic has to be reduced. Right. Uh, you can have a well-designed footballs, uh, that the, uh, motorcycle is no, that you cannot, uh, drive upon. Uh, and you can have. Uh, good signalized or even better block crossings, uh, where, uh, uh, you, if you didn't have that and somebody was trying to jaywalk, then the exposure would be much higher. Whereas now, by developing this crosswalk or painting this crosswalk, at least at the wake of the vehicles expect that there might be people who are trying to cross the road. Uh, these are, uh, effective in certain locations, not effective in others. The photo bridges. And also, uh, you may have shared use parts with bicyclists that reduces their exposure to the vehicles. So these are different means of, uh, uh, improving pedestrian safety, uh, is speed. Regular speed has been, uh, noted as one of the major factors, uh, contributing towards, uh, pedestrian injuries and pedestrian fatalities. So how do you reduce, uh, pedestrian, uh, or regular speed? Um, by design measures, uh, you may have, uh, um, uh, speed tables, right? Uh, rather than speed humps nowadays, you would see that there are speed tables that are in place, um, uh, that are more effective in reducing, uh, speed at intersections. Uh, you may have curb extensions that are actually, uh, now, uh, reducing, uh, the width. Uh, off the crosswalk, uh, that people have to cross the road. Now, instead, if the car was straight now, they would have to cross that additional distance. So usually curb extensions are provided, uh, to reduce the distance and by providing this curve extension, uh, the, the lane, uh, the, uh, the driver who is driving on the, uh, uh, on the lane, uh, fields that. Uh, the road, the road is narrowing and, uh, this feeling of road narrowing usually reduces their speed. Right? You will see, uh, deliberately that some of the low speed roads have a lot of, uh, horizontal curves in them, right? So these are different ways then obviously you have speed, speed humps that allow in traffic calming, uh, traffic coming usually is, uh, something which is associated with reduction of regular speeds. Uh, improving, uh, visibility of pedestrians, right? Not only do you have to have a good, uh, roadway lighting, uh, maybe you have to have a pedestrian signals as well. That allows vehicles to understand that, uh, this intersection has heavy pedestrian volume and hence they have to be, uh, they have to be on the lookout for pedestrians while they are crossing that intersection. Uh, at nights it is usually recommended that. Um, even if the pedestrians don't wear vests, uh, that are usually worn by, uh, construction workers, but, uh, you have to wear clothing that is at least, uh, bright in color so that when you're trying to walk bright and retro reflective some, some reflectivity, if it has, then if you're walking in darker areas as well, uh, through the headlights of the vehicles, they will be able to detect you. Uh, and also, uh, such physical objects, um, that are present very close to intersections where, uh, people would not be able to, uh, or the vehicles would not be able to see the pedestrians walking here are also sometimes removed from, uh, walkways or, uh, sidewalks and so on and so forth.