The intersection clearance time results have been calculated by ARRB / NTRO using computer simulation methods in accordance with the NHVR’s Performance Based Standards. The results are based on vehicle specifications (engine H.P., transmission and final drive ratio) typical for each vehicle type and include the effects of drivetrain losses, gear change time, tyre rolling resistance and aerodynamic drag. The results are indicative of the expected vehicle acceleration performance and can assist road managers with making an access decision as part of a broader route assessment.
The heavy sight distance and acceleration assessment tool helps road managers assess the network access of PBS vehicles by comparing the acceleration performance of vehicles at intersections.
The tool calculates the times taken by the proposed vehicle to accelerate from rest and cross a major road carriageway, turn onto another carriageway (in the opposite direction of the first) and then accelerate to the speed of the traffic. The time taken by the proposed vehicle is then compared against the existing vehicle. The outputs include acceleration time, exposure, and relative risk. The calculations are based on the configurable intersection layout and the vehicle specifications.
Configure the intersection first and then select the existing and proposed vehicles to compare the results.
The proposed vehicle poses and requires , based on
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Uknown summary
| Name | Current | Proposed | Rel. Exposure |
|---|---|---|---|
| Time | Time | Risk % Change | |
| Complete turn | NA | NA NA | NA |
| - | - | - | - |
| Reach 70% target speed | NA | NA NA | NA |
| Reach target speed | NA | NA NA | NA |
Uknown summary
| Name | Current | Proposed | Rel. Exposure |
|---|---|---|---|
| Time | Time | Risk % Change | |
| Complete turn | NA | NA NA | NA |
| Clear near carriageway | NA | NA NA | NA |
| Reach 70% target speed | NA | NA NA | NA |
| Reach target speed | NA | NA NA | NA |
The results can be reported on the basis of payload (tonnes) or current number of trips per week.
The reported number of trips per week indicates the number of trips each vehicle would require in order to transport the freight task (as per the mode selected).
This section details the time taken for each vehicle to perform a certain task.
The turning movements travel into the nearest lane. This results in the configuration of the far carriageway not influencing the time taken to complete the right turn.
For right-turn movements, the subject vehicle only commences the turn when able to complete the turn in one movement. Vehicles do not stop in the median, or while blocking oncoming traffic.
The vehicles are modelled accelerating to 15 km/h, then travelling at 15 km/h until the vehicle is fully within the lane (straightened up in the direction of travel), and then accelerating from 15 km/h to the target speed.
Complete left turn: This is the time taken for the vehicle to complete a left turn into the near carriageway. The turn is considered to be completed when the vehicle is fully within the nearest lane of the near carriageway and straightened up in the direction of travel.
Reach 70% of the target speed, left turn: This is the time taken for the vehicle to complete the left turn into the near carriageway and then accelerate to 70% of the target speed. This value of 70% of the target speed can be considered to be an appropriate speed at which the exposure risk of rear-end type crashes has decreased significantly.
Reach target speed, left turn: This is the time taken for the vehicle to complete the left turn into the near carriageway and then accelerate to the target speed.
Complete right turn:This is the time taken for the vehicle to complete a right turn into the far carriageway. The turn is considered to be completed when the vehicle is fully within the nearest lane of the far carriageway and straightened up in the direction of travel.
Clear near carriageway: This is the time taken for the subject vehicle to clear the near carriageway when performing a right turn.
Reach 70% of the target speed, right turn: This is the time taken for the vehicle to complete the right turn into the far carriageway and then accelerate to 70% of the target speed.
Reach target speed, right turn: This is the time taken for the vehicle to complete the right turn into the far carriageway and then accelerate to the target speed.
The exposure is the relative value based on the difference in intersection clearance time between the subject and comparison vehicle. This provides an easily comparable value for the length of time that the subject vehicle is exposed to conflicting vehicles in relation to the length of time that the comparison vehicle is exposed for.
The Exposure does not take into account that a longer, heavier combination will typically require less vehicle movements to complete a freight task than a shorter, lighter heavy vehicle combination. The Relative Exposure Risk factors in the Freight Equivalence of the subject vehicle to provide a modified Exposure value, which takes into account the freight capacity of the subject and comparison vehicles.