An assessment of the deceleration on horizontal curve component of the Austroads operating speed estimation model

Noon, Jarred (2016) An assessment of the deceleration on horizontal curve component of the Austroads operating speed estimation model. [USQ Project]

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Abstract

This dissertation builds on earlier work by the Australian Road Research Board (AARB) and Austroads. Speed data was obtained for the Golden Highway in NSW and the 85th percentile speed was derived at the approach, start, middle and end of 96 horizontal curves sites in the Westbound direction.

The calculated curve design speed was plotted against the 85th percentile speed. The results support earlier work by (Mclean, 1979) and showed that drivers are still
willing to tolerate higher values of side friction when travelling at speeds less than 100km/hr and that on horizontal curves suitable for 100km/hr or more that drivers tend to travel at a more uniform speed.

The potential variables affecting a vehicle’s operating speed were recorded at each of these horizontal curve sites. Multivariable regression analysis was undertaken to determine what variables were statistically significant to a vehicles operating speed as it traverses a horizontal curve. These variables were found to be longitudinal grade (+3% or more and -4% or less), horizontal curve length (700m or more), vertical geometry (crests) and whether stopping sight distance was achieved. Sites with variables exceeding these values were excluded.

The remaining factors contributing to a vehicle’s speed as it traverses a horizontal curve were approach speed and horizontal curve radius. The radius of the remaining data was plotted against 85th percentile vehicle speed at the start, middle and end of each of the remaining horizontal curve sites and confirmed that the maximum deceleration occurs at the middle of the horizontal curve.

Sites that experienced an increase in 85th percentile vehicle speed at the midpoint of the horizontal curve (relative to the approach speed) were removed and the radius of the remaining data was plotted against curve midpoint speed for each separate banded approach speed and compared to earlier prediction models. Similarly to recent research by Austroads it was found that that the current Austroads deceleration on horizontal curves model provided a conservative representation of the operating speeds of vehicles. It is recommended that further research be done into the effects of these roadway characteristics on operating speed with the aim of developing correction tables. A new deceleration on horizontal curve speed prediction relationship was produced for 100km/hr approach speed. This relationship could potentially be used to help update the current Austroads deceleration on horizontal curves graph.


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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Honours) Major Civil Engineering project
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying
Supervisors: Ayers, Ron
Date Deposited: 21 Jul 2017 02:25
Last Modified: 21 Jul 2017 02:25
Uncontrolled Keywords: deceleration; horizontal curve component; Austroads operating speed estimation model; multivariable regression analysis
Fields of Research : 09 Engineering > 0905 Civil Engineering > 090599 Civil Engineering not elsewhere classified
URI: http://eprints.usq.edu.au/id/eprint/31453

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