Determining the upgrades and design speeds that two-lane highways don’t require climbing lanes

The relationship between the design speed and the value of two-lane highway upgrade has a significant importance in determining whether this part of highway requires a climbing lane or not. climbing lanes are added to ensure not reducing the safety on the highway,because the reduced speed of trucks on the upgrade results in obstructing the traffic behind them. codes and references illustrated the cases when climbing lanes must be added in graphics,but these cases are limited by specific characteristics of trucks and specific design speeds. this leads to limitation of applicability of the graphics. in this research,general relationships that relate the value of upgrade to the design speed and to the predominant truck characteristics are concluded. these relationships are applicable for design speeds between 40 km/h and 130 km/h and for different truck characteristics. this makes them have a wider range of usage than the graphics included in the current codes and references. © 2017 just. all rights reserved.