Performance Indicator for Two-Lane Intercity Highways under Heterogeneous Traffic Condition

:Performance evaluation of two-lane intercity highways helps in defining the level of service (LOS) being provided to the road users and making a decision regarding utilization of public funds. In the past, different performance measures were proposed by different researchers to assess the performance of two-lane highways. In the present study eight performance measures and four platooning variables are examined in order to identify the best suited performance measure for two-lane intercity highways under heterogeneous traffic condition. Free-flow speed is calculated by using the 10 sec gap threshold value which implies that the vehicles will be in free flow condition if they travel with the gap value equal to or greater than 10 sec. Gap acceptance curve method is used to identify the followers with the help of speed difference limit ranged from -4 to +10 km/h and 10 sec gap threshold value. Different critical gap values are observed ranged from 1.9 to 4.3 sec at different study sites beyond which the probability of vehicles to travel in free flow condition will be more. Afterwards different graphical and statistical analyses are carried out to understand the association between the eight performance measures and four platooning variables. Among all the platooning variables examined, two-way traffic volume has the highest correlation with all the performance measures. The study revealed that the speed related performance measures are not appropriate to examine the performance of two-lane highway because of their less sensitiveness towards platooning variables. On the other hand, follower related performance measures have the highest correlation with two-way traffic volume. Therefore, number of followers per capacity followed by follower density are found to be two most effective measures for evaluating the performance of two-lane intercity highways under heterogeneous traffic condition.