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Webinar Question and Answer Transcript

Signal Control Priority and Alternative Intersections in Connected Vehicle Environments
(April 22, 2021)

T3 and T3e webinars and T3e webinars are brought to you by the Intelligent Transportation Systems (ITS) Professional Capacity Building (PCB) Program of the U.S. Department of Transportation’s (USDOT) ITS Joint Program Office (JPO). References in this webinar to any specific commercial products, processes, or services, or the use of any trade, firm, or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the USDOT.


Q.

For the CV what was the distance range assumed for the OBU?

A.

Zorica Cvijovic: So, in both operations we didn’t have fixed distance from vehicle to vehicle requests priority. It depends on the time the vehicle needs to reach intersection, so if vehicle up to 50 seconds to the intersection then there are two conditions. If there is some kind of lateness or if it is high number of passengers on board vehicle will be able to request priority. So it is not fixed by distance like by conventional single priority when we have fixed position.

Mutasem Alzoubaidi: In my study of intersection we actually used 1,000 feet which is the DSRC range that is known by and that connected vehicles can communicate up to 1,000 feet, so that is the distance we have used.

Q.

These appear to be virtually all simulations—did you calibrate with actual field data collection and CV experience?

A.

Mutasem Alzoubaidi: Yes, I am positive we have both calibrated our models with actual field data. So for my study I have calibrated then with traffic volumes that were provided by UDOT. And I also think Zorica has also calibrated both her models for the TSP and FCP based on UDOT data and Wyoming DOT data.

Q.

We know that CFIs have a very large footprint because of the buffer space that needs to be implemented to separate directions. How do you see for example how the CV vehicles will actually change that in the future? Can we go to a smaller footprint when we have more connected vehicles in the roadways?

A.

Mutasem Alzoubaidi: There are usually several alternatives of unconventional design that could replace a conventional intersection in a specific location. Comprehensive operational and planning studies are conducted include planning a scenario and comparisons that usually are conducted as parts of an agency’s plan to solve traffic issues at a specific location. If a study concludes that the CFI should be implemented, then this study would have also taken into consideration the right‐of‐way part of the study. According to one study that was intended to compare the operational performance of seven unconventional intersections. They are namely: the quadrant roadway, median U‐turn, Super Street, bow tie, jug handles, flood street intersection, and the CFI. It was found that the CFI requires the least right‐of‐way among these alternative intersections. Also, from previous studies, it focuses on how connected vehicles can reduce lateral clearance between vehicle clearance and headway in spacing. I would say more relatively compact designs could be expected because of CFI signal deployment. However, in terms of turning lanes, if the intersections are designed to accommodate larger vehicles, then at those specific locations within the same intersections, then the required right away would be governed with the provision of a safe turning radii at the turning intersections of the intersection. I would say maybe due to decreased lateral links and headways in spacing, we may can expect some relatively compact CFIs as a result of CV deployment. This is still an interesting question that could be answered with deeper research.

Q.

Did your TSP deal with queue during peak traffic—and how did you detect the queue?

A.

Zorica Cvijovic: So, out of the reasons TSP algorithm which is for the regular buses, it uses Queue conditions during peak hours of criteria to grant priority. Microsimulation has options to set Queue conditions. It is based on the number of vehicles in front of the vehicle and the speed. For the model where we had the DOT, we didn’t use the Queue conditions because the vehicles have a separate lane.

Milan Zlatkovic: I believe when you are working on the algorithms, we are using the position of the vehicle and the speeds and we were able to know exactly how far away the vehicle was from the intersection. That gave us the idea about the queue based on the speed and based on the distance from the intersection. To elaborate a little on the answer.

Q.

What do you suspect will happen when V2V occurs versus V2I?

A.

Mutasem Alzoubaidi: One study has been conducted previously that has actually compared vehicles equipped with adaptive cruise control versus vehicles conducted with communicating adaptive cruise control—and there were notable differences between the operational and safety performance of the communicating adaptive cruise control versus the adaptive cruise control. The communicating one has much, much better influence on operations and safety. I don’t remember the numbers but this was a relatively new research. Yes, I think they are expected with notable differences.

Q.

At 25% MPR to what do you attribute the difference in “speed” between CV and non CV? It would seem CV’s would be constrained to travel at the same speed as the non CVs, but perhaps CV’s were stopped less frequency than their proportion of the traffic.

A.

Milan Zlatkovic: I will help with this. Even with 25% of NPR, a quarter vehicles are equipped, we were able to see some change between the vehicles. For example, we might have one non‐CV and three CVs in a row. And then maybe seven or eight non‐CV vehicles. We still do a little bit of platooning. Whenever we have some platooning, we always have reduction in headways between the vehicles and they travel a little bit more at the harmonized speeds. There is not so much speed difference. I believe this is where some of that difference in speech would come, even with very low market penetration rates. And as you can see it changes quite significantly especially if you go 50 and up. This is where there is a significant change in a lot of parameters.

Q.

We did use Latin long coordinates for the vehicles and simulation. What would that mean for practical implementation because we are trying to do something that can be implemented in the field? Can you briefly elaborate on that?

A.

Zorica Cvijovic: One of the main pieces of information in basic safety messages used for communication with traffic signals total side units, is latitude and longitude coordinates. Roadside units contain the coordinates for the center of the inspection which are used as a reference point. As vehicles approaching the intersection, it sends lat and long coordinates and they compute the current distance in every time step. This distance is later used in the algorithms, and together with the actual vehicle speeds, it is used to define a time that the vehicle needs to reach the intersection. It is one of the main ways to grant priority. With some additional settings in reason when the coordinates are set to be converted to coordinates. It means those models and all algorithms and control settings are transferrable in the field with minimum or no adjustments. What makes those models very to have high fidelity?

Q.

How long did it take to get your RSU registered with FCC?

A.

Milan Zlatkovic: Interesting question. We did not do a field implementation. We are working with UDOT trying to see if we can expand a little bit on their actual systems because they have one of the bus corridors but they already have this implemented. It is more of a practical implementation. We actually did not have any kind of field implementation. We just analyzed this and simulation. We did not have to go through that process and I cannot really answer that question. We will see how it goes down the road when we start working on practical implementation for the systems.

Q.

Did you calculate the total delay reduction in the corridor for the peak hour?

A.

Zorica Cvijovic: I can pick up this one since I have corridor. In our case we have some inspections between intersections. For each of the sections we calculated and used Rh value for all of them.

Mutasem Alzoubaidi: For my corridor it was similar. We calculated all of the delays for each intersection separately. We did have so many results. But we presented is only to affect the presentation slides. We could have done much deeper but that would be much more to present in one presentation. We have so many delayed reductions for the corridor. I think it applies to both cases as well.

Q.

What are going to do now, that the lower 45‐MHz of the DSRC frequency has been allocated to unlicensed indoor and outdoor wireless in the next 12 months?

A.

Milan Zlatkovic: I can discuss that. That range that was originally allotted to this vehicle to vehicle communication has been changed because of some new roles. When it comes to the algorithms which we developed, it doesn’t matter which type of communication we use. As long as we have the information about the vehicle position, vehicle speed, and for public transit, if we know the information about the number of people on board, that is all we need. We don’t worry about the type of communication as long as weekend send that information to the system. It doesn’t really matter. The algorithms will work the same way. We did a study a few years ago where we use GPS systems from transit vehicles. We were able to develop similar algorithms as we have here by using a GPS information from transit vehicles. The communication system in the algorithm is not that important as is the algorithm itself. Once it has the information it needs, then it can do the job it was intended to do. I hope this clarifies. We don’t have any practical experience with the communication systems. Mostly what we are trying to do here is to do—develop the algorithm that can help some of the special control priority operations or to help us with the improving operations and safety at innovative design.

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