01555404

Component

Studying the relation between different geometric features and roadway capacity is very important and can lead to significant improvements in the planning and design stages. The main objective of this research is to model the relation between the different geometric features of the horizontal alignment with the capacity of tangent and curved elements of two-lane two-way highways and, more importantly, to model the capacity loss between tangent and curved elements. Traffic and geometry data were collected from six rural two-lane two-way sites on Benisuif - Assiut Agricultural Road in Egypt. Each site is composed of two elements; a straight element (tangent) and a succeeding horizontal curve .The capacity for each element was estimated using extrapolation from flow-density fundamental diagram. Using regression analysis, different models were developed. For tangent elements, the results show that as the carriageway width increases, the capacity also increases. For curved elements, the capacity increases by increasing of horizontal curve radius and carriageway width. With regard to capacity loss, the capacity loss decreases by increasing of horizontal curve radius and carriageway width of curved elements. It is noticed that at horizontal curve radius greater than 900m, there is no loss in capacity. In addition, the results show that the passenger car unit (PCU) values for vehicle categories increases linearly with increase of carriageway width. The resulting models are useful for optimizing geometric design on two-lane two-way highways from the capacity point of view to provide a consistent and flowing highway at a suitable level of service, avoiding significant capacity loss on sharp horizontal curves.

This paper was sponsored by TRB committee AFB10 Geometric Design.

01550057

15-1439

English

14p

2015

Transportation Research Board 94th Annual Meeting

Digital/other

Figures; References; Tables

Geometric design; Highway capacity; Highway curves; Regression analysis; Rural highways; Tangents; Two lane highways

Horizontal alignment

Egypt

Design; Highways; I20: Design and Planning of Transport Infrastructure

Transportation Research Board Annual Meeting 2015 Paper #15-1439

TRIS, TRB, ATRI

Dec 30 2014 12:33PM