When do Bus Rapid Transit systems make congestion worse?

Harmoni_Central_Busway_Transjakarta_1
A bus station in central Jakarta, via Wikipedia

That’s the question posed by a recent(ish) VoxDev article by Arya Gaduh, Tadeja Gračna, and Alexander Rothenburg.  They studied this topic in Jakarta, and found that the TransJakarta BRT system took lanes away from cars without attracting enough passengers to substantially reduce the number of cars on the road.  This is also due partly to the fact that the popularity of motorcycle taxis soared over the implementation period, pulling many people off public transit entirely.

What are the implications for African BRT projects, like those in Nairobi, Accra, or Dar es Salaam?  One clear takeaway is that the effect of the BRT system depends on the quality of its implementation.  As the authors note,

A ‘gold standard’ BRT in Curitiba, Brazil, includes GPS-based service planning, multiple networked routes, peak frequency buses, comfortable stations, and feeder bus integration. On the other hand, Lagos’ BRT lacks off-board fare collection and platform-level boarding at stations, and does not meet basic international BRT standards. Overall, more BRTs are similar to the latter than the former…

As a result, how a BRT system impacts congestion and travel time varies across settings. Findings from the experiences of systems such as those in Bogota, Lahore, or Mexico City demonstrate that a well-implemented BRT can increase public transport use, reduce air pollution, and increase output and labour market access (Tsivanidis 2019, Majid et al. 2018, Bel and Holst 2018). On the other hand, poor implementations have led to failure and eventual disbandment in the case of BRT systems in Delhi and Taichung (Pojani and Stead 2017).