GPS-fitted buses operating in bus rapid transit systems (BRTS) ofKeywords: Bus rapid transit systems, GPS data, route performance, statistical parameters.PUBLIC transportation systems like bus rapid transit system (BRTS) are becoming popular all over the world because of their strong identity and low initial investment 1,2 . Satiennnam et al. 3 reported that BRTS has the capability of bringing a significant modal shift from private vehicles. BRTS are running in eight cities of India 4 ; buses running in these systems are mostly GPS-fitted which helps in collecting a wealth of travel-time data, but the methodologies to use the same for performance evaluation and system monitoring are limited. This article evaluates the performance of BRTS using the aforesaid GPS data for two routes in Ahmedabad. Both the selected routes operate from the innermost part of the city and then extend to the outer areas. These routes are majorly segregated from the normal traffic, but wherever sufficient right of way was not available, the buses were running with mixed traffic. It is thus important to evaluate the performance of such routes and carry out a segmentlevel analysis. Further, we have compared travel-time reliability of a BRTS and a non-BRTS route having similar characteristics in terms of land use and right of way. This was done to show the advantage of BRTS corridor in terms of travel-time reliability. Finally, after route evaluation we present a travel-time reliability and stabilitybased network level of service analysis. This was based on two indices, i.e. how the level of service had changed from 2013 to 2016 with the changing corridor length from 61 to 89 km.
Literature reviewStudies in the past have reported using GPS data for various analyses in a bus transit system. The initial studies used GPS data to estimate travel time from the bus location data 5 . After developing techniques for travel-time estimation from GPS data, historical data were utilized for predicting travel time using artificial neural network and Kalman filter method 6,7 . Using the travel-time estimation, average commercial speed of the buses was also estimated 8 . After the travel-time estimation and prediction studies, the travel-time variability (TTV) and reliability studies were reported 5,9-12 . Day-to-day and period-toperiod travel-time reliability analysis was also carried out earlier 13 . GPS data were used to develop transit level of service based on the criterion of 'on time performance', in which the percentage of vehicles not arriving on time was computed by considering a vehicle to be on time if it was not more than 5 min late or 3 min early 14 . In another study, a new form of level of service (LOS) criterion was suggested based upon the weighted delay and acted as improvement over the conventional Transit Capacity and Quality Service Manual (TCQSM) 14 level of service ranges 15 . GPS data were also used to evaluate bus priority system; for which they were fed into a simulation software for carrying out sensitivity analysis 16 .