estimation of operating speed on two lane two way roads along n-65 (sibi –quetta)

present study is an extension of earlier work carried out on two-lane two way roads in the two provinces of pakistan i.e. n-25, n-55 and n-5 regarding the measure of operating speed and development of operating speed prediction models. curved sections of two-lane rural highways are the main location of run-off road accidents. in addition to that the road alignment having combination of geometric elements may be more harmful to the drivers than the successive features with adequate separation. this study is carried out on two-lane two- way road along n-65 (from sibi to quetta). three sections are selected for study with thirty three horizontal curves. continuous speed profile data was recorded with the help of vbox (gps based device) which was attached with a vehicle to detect vehicle position through satellite signals. vbox is new equipment with modern technology in this field and it helps in recording continuous speed profile and saving of this information on the computer as a permanent record. through the regression analysis, models were developed for estimation of operating speed on horizontal curves and on tangent, and estimation of maximum speed reduction from tangent to curve. the validation of developed model shows compatibility with the experimental data.