Overview

This Function shall be capable of providing the following facilities:

(1) The ability to provide support for the Driver by suggesting the optimal speed and headway for the Host Vehicle in both its current and expected locations in the road network.
(2) In a suitably equipped Host Vehicle, the ability to enable it to automatically keep at or below the optimal speed (Intelligent Speed Adaptation - ISA) and headway.
(3) Once the optimal speed and headway have been determined, the ability to send them for display to the Driver, to the Other Vehicle via the Vehicle Communications Function and to the Monitor Vehicle Safety Behaviour Function.
(4) The ability to ensure that the optimal speed is always less than or equal to the legal speed limit and enable it to vary from one road segment to another.
(5) When sending the optimal speed and headway for display to the Driver, the ability to provide the reason(s) for any changes in the suggested speed and/or headway.

Functional Requirements

(a) continuously monitor for receipt of the vehicle position for ISA, inter-urban and urban speed settings, legal speed limit for ISA, weather conditions for ISA, ISA information and vehicle data for determining speed & headway data flows
(b) when in (a) the ISA information data flow is received from the geographic information provider, load the speed limit that it contains into the store of ISA Data
(c) when in (a) the legal speed limit for ISA data flow is received, load its contents into the store of ISA Information Data
(d) when in (a) either of the inter-urban and urban suggested speeds and headways data flows are received, store the data internally for future use
(e) when in (a) the weather conditions for ISA data flow is received, store its contents internally for late use
(f) when in (a) the vehicle data for determining speed & headway data flow is received, store its contents internally for future use
(g) when in (a) the vehicle position for ISA is received use its content to determine which of the speeds received in (b), (c) or (d) is the lowest and using the weather conditions received in (e) plus the vehicle data received in (f) calculate the optimum speed for the vehicle
(h) as a result of (g) calculate the vehicle headway again using the weather conditions received in (e) plus the vehicle data received in (f)
(i) if the answer to (h) is that the calculated headway is greater than that received in (d) use it in the data that is sent in the output data flows
(j) send the results of (g) and (i) to the Display Current Speed Limit function using the current suggested speeds and headways data flow, to the Vehicle Communications function in the suggested speeds and headways from ISA data flow and to the Monitor Vehicle Safety Behaviour function in the suggested speed and headway for safety behaviour data flow
(k) also as a result of (g) send the ISA acknowledgement data flow to the Prepare Extended Floating Car Data function.

Diagrams

Parent Higher Level Function

• 5.13 Provide Vehicle Data and ISA

Input logical dataflows

• fesp.g-ISA_information
• fws-weather_conditions_for_ISA
• mt.pshvs_inter-urban_suggested_speeds_and_headways
• mt.pshvs_urban_suggested_speeds_and_headways
• pshvs_legal_speed_limit_for_ISA
• pshvs_read_ISA_data
• pshvs_vehicle_data_for_determining_speed_&_headway
• pshvs_vehicle_position_for_ISA

Output logical dataflows

• pshvs_current_recommended_speeds_and_headways
• pshvs_ISA_acknowledgement
• pshvs_load_ISA_data
• pshvs_suggested_safe_speed_and_headway
• pshvs_suggested_speeds_and_headways_from_ISA

User needs