  Since ride-hailing has become an important travel alternative in many cities
worldwide, a fervent debate is underway on whether it competes with or
complements public transport services. We use Uber trip data in six cities in
the United States and Europe to identify the most attractive public transport
alternative for each ride. We then address the following questions: (i) How
does ride-hailing travel time and cost compare to the fastest public transport
alternative? (ii) What proportion of ride-hailing trips that do not have a
viable public transport alternative? (iii) How does ride-hailing change overall
service accessibility? (iv) What is the relation between demand share and
relative competition between the two alternatives?
  Our findings suggest that the dichotomy - competing with or complementing -
is false. Though the vast majority of ride-hailing trips have a viable public
transport alternative, between 20% and 40% of them have no viable public
transport alternative. The increased service accessibility attributed to the
inclusion of ride-hailing is greater in our US cities than in their European
counterparts. Demand split is directly related to the relative competitiveness
of travel times i.e. when public transport travel times are competitive
ride-hailing demand share is low and vice-versa.
