The effect of bicycle taxis on capacity of mixed traffic urban roads : a case study of Kisumu town in Kenya

Bicycle taxis, also known as boda boda, provide a flexible and convenienttransportation service to residents of Kisumu city in Kenya. The boda bodashare the road carriageway with both motorised modes and handcarts andaccounts for 60% in traffic modal split and transports about 32.2% of thepassengers in the city. The increasing popularity of boda boda over the lastfew years has brought to the forefront a problem related to increased bicycletaxi traffic- that of estimating the capacity of the mixed traffic roads.Capacity is a fundamental traffic flow characteristic that is essential forplanning, design, and operation of roads transport systems. Prediction andknowledge of capacity provide the basis for among others, optimisation ofexisting facilities and provision of more lanes or segregation of the differentmodes.To standardise the various transport modes with varied characteristics forthe purposes of capacity determination, passenger car is used. As is the casefor large vehicles, each boda boda in mixed traffic roads displaces several ora fraction of passenger cars in the flow. The number of passenger carsdisplaced under specific conditions is termed ""the passenger car equivalent""or PCE for those conditions.In recent years a few studies have been done on determination of PCE forvehicles in mixed and heterogeneous flow conditions. This research thesispresents and extends on these studies by determining the PCE values forvarious modes plying Kisumu city, which although mixed flow in natureexhibits characteristically different flow when compared to other places likein Asian cities where the dominant two-wheeler mode is motorised.Based on the study from many literature sources, this research adopts themodified speed method to determine PCE values on road sections and majorroads intersection approaches. With the PCE values of each mode, theireffects on the road capacity, relative to the standard passenger cars, areestablished based on the field data using empirical regression analyses.Most intersections in Kisumu city are unsignalised. Capacities of minorroads in unsignalised intersections are commonly analysed based on gapacceptancetheory whereby capacity is considered as a function of theavailability of critical gaps or in general acceptable gaps that can allowentry of vehicles into a particular traffic stream. This study adopts the gapacceptancetheory from which critical gaps are determined whence minorroad capacity.The study applies the modified Raff method to determine the critical gapsat the road intersections that are used to establish the minor road capacityeffect of each vehicle type using the negative exponential headwaysprobability distribution method.From the study it was established that bicycle taxi does enhance the roadcapacity by increasing it whereby the higher the bicycle proportion, thehigher the capacity. In addition it was also established that the presence of bicycles on the major road at a T-intersection enhances the potentialcapacity of the minor road.Included in this thesis are a review of relevant and related literature, adetailed explanation of field data collection, methodologies, analysis andresults and finally conclusions and recommendations