1 Introduction
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Does carrying the take-over maneuver in advance to the roadworks vertical signage foster an enhancement in Traffic Efficiency across the bottleneck section?
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If the C-ITS broadcasts what is the closed lane and allows vehicles on the open one to keep on driving in the automated mode does the overall traffic flow benefits from that in terms of Traffic Efficiency?
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What are the impacts on the upstream section in terms of delay?
2 Bibliographical study about take-over times and the possible L3 vehicle behaviour
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The HC vehicle receives the C-ITS messages or is made aware of the roadworks through vertical signaling. Either way, the vehicles start the take-over transition which is accomplished within the software by changing the vehicle type and, consequently, its behavior.
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A vehicle that has Take-Over transition as vehicle type, is forbidden to perform a lane change as long as it remains in said vehicle type container, the driving behavior is still similar to the L3 one and the vehicle keeps on driving itself until the human driver is in the loop again.
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As soon as the Take-Over interval has passed (on the basis of the simulation seconds), the human driver is considered out of the initial phase ranging between 10 and 15 s, as found from literature, and able to perform a lane change. This is simulated through another change of the vehicle type, that now is ruled by a human behavior and no more by the behavior of an automated vehicle. Moreover, through VISSIM settings, it is imposed that this vehicle type wants to perform a lane change as soon as the take-over interval has passed (which reflects the input of the C-ITS message, closure of a lane due to roadworks).
3 Modeling framework
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The L3 vehicles are the only ones able to receive the C-ITS message; no traditional vehicle receives the information about the lane closure downstream.
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In both the C-ITS scenarios (range 696 m and 1500 m), the L3 vehicles on the open lane are able to keep driving because, to enter the roadwork, no lane change is required. From section 1 until the start of the roadworks, these vehicles will not enter the closing lane.
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In both the C-ITS scenarios, the L3 vehicles on the closing lane receives the message and start the take-over maneuver, in order to re-engage the human driver. How this take-over transition is managed through the software is explained in the following.
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The vehicles unequipped for the reception of cooperative messages discover about the lane closure when reaching section 4, 336 m ahead the lane closure. This reflects the vertical signals ahead a roadwork designed in the simulation.
3.1 Simulated scenarios
3.2 COM Interface – modeling a take-over transition in PTV VISSIM
3.3 Driving behavior and modeling parameters
4 Scenario outputs and results
4.1 No C-ITS scenario
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The driving logic implemented is considered quite realistic, based on previous work [1, 19]. In fact, the time gap of 1.2 s is not a strong hypothesis and neither is the perfect compliance to the speed limits for L3 vehicles (this compliance is not kept by traditional vehicles, as explained in [13]). Moreover, the lane change of the Highway Chauffeur vehicles was tuned to be more conservative than the one performed by the traditional ones (the Min. Headway value is kept 1 for both types while the Safety Distance Reduction Factor is equal to 0.6 for traditional vehicles end to 1 for L3 ones).
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The aim of this paper is not to estimate the impacts related to automated driving on the traffic flow. Instead, the aim is to frame the different impacts on Traffic Efficiency of the three described scenarios bound to the joint implementation, simulated with the same driving behavior for each vehicular class. Therefore, the effects of a certain time gap for L3 vehicles rather than of a certain lane change aggressiveness becomes less relevant for the discussion, being kept consistent through all the scenarios.
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The benefits arising from the presence of L3 vehicles should not overshadow the negative impact on safety that a high number of take-over maneuvers could entail. This paper does not describe these impacts since they can hardly be framed through the exploited tools, still it is worth highlight them to give the reader a complete picture.
4.2 Jointed scenario 1 (696 m)
4.3 Jointed scenario 2 (1500 m)
5 Scenario comparison
10% | 33% | 50% | 66% | 80% | 100% | |
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NO C-ITS | 23.26% | 23.84% | 22.54% | 22.57% | 19.54% | 14.25% |
696 m | 17.34% | 15.81% | 12.65% | 11.47% | 9.69% | 8.27% |
1500 m | 18.61% | 14.36% | 11.93% | 10.26% | 9.68% | 8.75% |
6 Conclusion
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Does carrying the take-over maneuver in advance to the roadworks vertical signage foster an enhancement in Traffic Efficiency across the bottleneck section?
-
If the C-ITS broadcasts what is the closed lane and allows vehicles on the open one to keep on driving in the automated mode does the overall traffic flow benefits from that in terms of Traffic Efficiency?
-
What are the impacts on the upstream section in terms of delay?
MP | 10% | 33% | 50% | 66% | 80% | 100% |
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Average Delay | 23.26% | 23.84% | 22.54% | 22.57% | 19.54% | 14.25% |