Toward an operating speed profile model for rural two-lane roads in Egypt

Operating Speed Prediction Model as a Tool for Consistency Based Geometric Design of Four-Lane Divided Highways

“…Vehicles not influenced by environment vehicles are considered as free flowing. Only highway geometry influences the speed of free flowing vehicles (Hashim et al 2016;Polgár et al 2013;Tettamanti, Varga 2014). Hence, the free flow speed is defined as the speed adopted by a driver uninfluenced by other vehicles in a traffic stream for a given road conditions (Polgár et al 2013;Tettamanti, Varga 2014).…”

“…The Highway Capacity Manual (TRB 2010) suggests that vehicles travelling with headway equal to or greater than a threshold headway value are considered as free flowing. For rural highways, several researchers have adopted the threshold headway value as 5 s (Fitzpatrick et al 2000a;Hashim et al 2016;Gong, Stamatiadis 2008;Poe et al 1996;Russo et al 2015Russo et al , 2016. However, weak lane discipline in multi-lane divided highways can influence vehicles (Mathew et al 2015;Mallikarjuna, Rao 2011;Gunay 2003Gunay , 2007Bangarraju et al 2016;Drew 1968;Case et al 1953;May 1959;Rawson 2015) prior to centre of the horizontal curve.…”

“…Therefore, the present study considers sharp curves with radius 500 m or below for developing speed prediction model. Most of the available speed prediction models are developed for two-lane rural highways (Fitzpatrick et al 2000a(Fitzpatrick et al , 2000bLamm et al 1990Lamm et al , 1998Hashim et al 2016;Abdul-Mawjoud, Sofia 2008;Abbas et al 2011;Jacob, Anjaneyulu 2013;Memon et al 2008). Table 1 represents the summary of a few relevant models.…”

“…However, availability of speed prediction model for four-lane divided horizontal curves is very limited, especially in developing countries. Generally, researchers have adopted Ordinary Least Square (OLS) regression technique for developing the speed prediction models (Misaghi, Hassan 2005;Fitzpatrick et al 2000a;Lamm et al 1990Lamm et al , 1998Hashim et al 2016;Abdul-Mawjoud, Sofia 2008;Abbas et al 2011;Eboli et al 2017;Russo et al 2016). The independent variables used in these models are combinations of curve radius, curve length, length of approach tangent, degree of curvature, deflection angle, gradient, lane width, shoulder AADT -average annual daily traffic; AG -approaching grade; ATL -approach tangent length; CL -curve length; FC -front curve index; G -gradient; LW -lane width; MSR -maximum speed reduction; MT -median type index; PC -point of curvature; STshoulder type index; SW -shoulder width; Δ -deflection angle; V a -approach tangent speed; V 85 -85th percentile speed; V 85 @ PC200 -85th percentile speed at 200 m before PC; V a_85 -85th percentile speed at approach tangent; V a_max -maximum approach tangent speed.…”

“…(Misaghi, Hassan 2005;Fitzpatrick et al 2000a;Lamm, Choueiri 1987). Further, in these models, the independent variable coefficients vary widely (Fitzpatrick et al 2000a;Lamm et al 1990Lamm et al , 1998Hashim et al 2016;Abdul-Mawjoud, Sofia 2008;Abbas et al 2011; Jacob, Anjaneyulu 2013).…”