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•Intelligent Traffic Signal System (I-SIG)
•An overarching system optimization application accommodating signal priority, preemption and pedestrian movements
•Transit Signal Priority (TSP) and Freight Signal Priority (FSP)
•Two applications that provide signal priority to transit at intersections and along arterial corridors as well as signal priority to freight vehicles along an arterial corridor near a freight facility
•Mobile Accessible Pedestrian Signal System (PED-SIG)
•An application that allows for an automated call from the smart phone of a visually impaired pedestrian to the traffic signal, as well as audio cues to safely navigate the crosswalk
•Emergency Vehicle Preemption (PREEMPT)
•An application that provides signal preemption to emergency vehicles, and accommodates multiple emergency requests
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Consider a system of traffic signals that is segregated into different traffic control sections. For example, assume Section 1 is in an area where there are commercial factories and warehouses and there is significant freight movement. The operating agency might decide to provide freight signal priority in this corridor by setting up a priority hierarchy that provides priority for rail and emergency vehicles first, then for freight vehicles over transit and pedestrians.
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In a different section of the systems, a section where there is significant transit and pedestrian travel might be given a higher level of priority than freight. The priority hierarchy in this section might be set up for rail, emergency vehicles, then transit, pedestrians, and then freight.
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A key capability of MMITSS is the ability to use connected vehicle data to OBSERVE performance of the system. A variety of performance measures can be observed, including volume, delay, travel time, throughput, stops, and other important measures. These measures can be classified by mode of travel and movement at an intersection or in the control section.
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The Core MMITSS features include:
•Intelligent Traffic Signal Control that is based on the awareness of equipped vehicles. Intelligent signal control includes signal actuation, gap out, green extension, dilemma zone protection, pedestrian accommodation, coordination, and congestion control.
•Traffic state, flow and performance observation. Performance observation is a powerful tool in the MMITSS dynamic mobility application.
•Priority control for multiple modes including emergency vehicles, transit, trucks and other special classes of vehicles and travelers – including pedestrians.
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An example: NTCIP 1211 – NCHRP 3-66 framework multi-priority request framework definition consisting of a Priority Request Generator and a Priority Request Server.
•Priority Request Generator: an on-vehicle system to compute the desired service time and update the request when approaching traffic signals.
•Priority Request Server: responsible for gathering requests and implementing priority policy.
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•Opportunity for additional improvements using signal coordination (which is a form of priority in MMITSS)
•ISIG will excel when there are no constraints for priority (TSP, FSP)
•Did not consider impact of pedestrians or interaction with TSP
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•Opportunity for additional improvements using signal coordination (which is a form of priority in MMITSS)
•ISIG will excel when there are no constraints for priority (TSP, FSP)
•Did not consider impact of pedestrians or interaction with TSP
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•Opportunity for additional improvements using signal coordination (which is a form of priority in MMITSS)
•ISIG will excel when there are no constraints for priority (TSP, FSP)
•Did not consider impact of pedestrians or interaction with TSP
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•MMITSS can provide improvements for specific modes, but it could impact the other modes.
•MMITSS will also excel when there are multiple priority eligible vehicles requesting special service. Existing systems only provide priority timing for a single vehicle at a time.
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•MMITSS can provide improvements for specific modes, but it could impact the other modes.
•MMITSS will also excel when there are multiple priority eligible vehicles requesting special service. Existing systems only provide priority timing for a single vehicle at a time.
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Nomadic devices
•Nomadic devices are probably not suitable for ISIG since the volume of traffic and the latency in cellular communications could be limiting factors
•Since DSRC is being used for safety applications, ISIG can listen for BSM messages at an intersection with little additional effort.
Level of Market Penetration
•EVP and TSP are low hanging fruit as these fleets are generally owned and operated by public agencies.
•FSP is similar, but the fleet is diversely owned and operated.
•Early results indicate that about 25% market penetration is needed for ISIG and PERF MEAS
•PERF MEAS could be effective with lower market penetration if longer time frames are considered (to get several observations)
Possible Effects of Communication Errors and Latency
•The use cases for priority requests (EVP, TSP, and FSP) include acknowledgement confirmation, so random communication loss should not have an impact unless complete loss occurs.
•A few seconds of latency in the priority use cases will only result in slight impact to performance.
•Latency in ISIG can impact the Dilemma Zone protection and signal performance.
The marginal benefit with data from existing sensors
•ISIG benefits from existing detection when the market penetration is low (or when the traffic volume is low and market penetration is medium)
•Vehicles need to be observed (detected) to alert the controller that a vehicle needs to be served.
•Current EV and TSP sensors provide some level of data that can be used in priority applications, but the standards (SAE) support system level interoperability and the algorithms (EVP, TSP, and FSP) are more advanced than existing algorithms
The modal benefits of connected vehicle data are critical
•Knowing that a vehicle is transit, truck, or EV can significantly impact the ability to provide safe priority
•Signal control can benefit significantly using connected vehicle data to measure queue length, saturation flow rates, startup lost time, etc. These measures are not available without CV data
•Pedestrians (and bicycles) will be significant beneficiaries (using cellular)
•Performance observation is not possible without CV data [This could be one of the biggest benefits and doesn’t depend on only MMITSS – it should be part of every DMA]
Potential Deployment Impacts
•Near Term Impacts
•Significant benefits for priority control: EVP, TSP and FSP – in an integrated, multiple vehicle environment
•Mobility for disable pedestrians using the PED SIG application
•Mid Term Impacts
•Performance Observation by Mode (near term for EVP, TSP, and FSP)
•Improved Signal Control (ISIG) as market penetration increases
•Long Term Impacts
•Reduced dependence on complex infrastructure based detection systems (only 1 RSE required)
•Ability to adjust traffic control policy (priority) based on mode (and movement)
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