|M.Sc Student||Mattar Caroline|
|Subject||Developing Models for Consistent Design of Highways|
|Department||Department of Civil and Environmental Engineering||Supervisor||Professor Abishai Polus|
The goal of this research was to develop a model to evaluate the design consistency of two-lane rural highways. This is done by evaluating the speed reduction for successive geometric elements and length evaluation of the speed deviation from the average speed.
For this purpose, two measures were developed to evaluate consistency. The first was the normalized relative area limited by speed profile and average speed. The second was the speed standard deviation from the average speed. Criteria were developed for theses two measures to evaluate road design level and to classify it as a good, fair or poor design.
Following the development of the measures, a model for evaluation of highway consistency was developed. To calibrate this model, 11 Israeli highways were chosen; most were two-lane highways and two were four-lane highways.
To check the relationship between consistency and safety, accident rates data combined with geometric parameters, of nine two-lane rural highways were collected. For each highway, the average predicted speeds for curves and tangents and consistency were computed by a computer program (C-SpeedS) that was developed during this research.
Relationship between consistency versus accident rate and consistency versus average speed were developed. It was found that higher consistency levels increase the average travel speeds. In addition, it was found that when the design consistency is good, the accident rate decreases significantly.
In summary, a highway consistency model and criteria for evaluation of design levels developed and presented and a direct relationship to safety was shown. This enables road designers to check and compare various roads and to choose the alternative that has a higher consistency value.