Comparing operating speeds for incremental and leapfrog investment strategies in bus-based transit in South Africa

Abstract

The world is currently grappling with congestion problems that have affected the liveability of cities. Improvement in public transport has been one of the most sought-after solutions with implementation of Bus Rapid Transit (BRT) Systems being one of the key strategies. BRT infrastructure has spread to most of the world’s continents since its inception in Curitiba, Brazil. The implementation of BRT systems in South African cities has been made possible with the Public Transport Network Grant (PTNG).

The BRT systems in South African cities have been implemented on a leapfrog approach characterized with corridor level uplift following the full specification of Latin American BRTs to replace the existing minibus taxis (MBTs). This has been done in the cities of Cape Town, Johannesburg and Tshwane despite these cities having different characteristics such as land use, population densities compared to Latin American cities. On the other hand, Rustenburg has taken an incremental approach in which the existing MBTs have been scheduled and buses added to enhance capacity on certain routes. Other cities have come up with deviations from the conventional BRT such as BRT lite in Lagos (Nigeria) and buses of high-quality service in the municipality of George (South Africa). One of the key questions that emerges is what benefits cities attain from these strategies.

This dissertation compares the leapfrog and incremental approaches taken to improve public transport with an intention of achieving a complete BRT system as the final product. The incremental approach was envisaged to involve three interventions starting with scheduling of the existing MBTs, operating scheduled buses in mixed traffic and final introduction of BRT dedicated lanes with median stations. On the other hand, the leapfrog approach was envisaged to move from the existing MBTs to complete BRT corridor with dedicated lanes and median stations in a single step. This comparison of the two strategies is based on travel time savings as the benefit accrued from the interventions.

The study relies on empirical measurements of actual public transport operations to develop models of operating speed for the interventions. Rustenburg Rapid Transit (RRT) and Tshwane BRT are used as case studies. Ordinary Least Squares (OLS) models were calibrated and tested for conformity with OLS assumptions. Weighted least squares (WLS) was used to correct for heteroskedasticity while generalised least squares (GLS) was used to correct for both heteroskedasticity and serial corelation. The calibrated models were based on operating speed as the response variable while unsignalised intersections per kilometre, signalised intersections per kilometre, stations (stops) per kilometre and land use were predictor variables.

To illustrate their application, the developed models were applied to a theoretical 10 km corridor to estimate the operating speed and travel time under various interventions. Travel time was adjusted to account for variations in traffic congestion and passenger demand. Travel time savings were calculated as the difference between travel times for scenarios under consideration and the base scenario (no intervention). Results indicated that both incremental and leapfrog approaches provided positive time savings. The leapfrog approach provided maximum time savings under high demand and traffic congestion. All steps involved in the incremental approach provided a positive time saving. It is concluded that smaller cities and municipalities can follow an incremental approach while bigger cities can leapfrog to complete BRT.