A report out today suggests that Dublin's Luas service has led to big reduction in car usage among commuters living within its range.
But the Dublin Transportation Office report also found that the bus service was faring badly by comparison.
For people travelling within the Red and Green line areas, car usage is down by 21%.
Commuters said speed is the principal reason for the switch but also parking charges and traffic congestion.
The study found that around 33% of respondents also said the Luas influenced their decision to move into an area.
35% said they had made more journeys over the past two years because of the service, mostly for shopping.
But Dublin Bus seems to have become less desirable with its usage halving in the Luas areas.
Reliability of journey time was the biggest problem with the bus service. The Dublin Transportation Office suggests that travel information should be provided at bus stops in the same way as the Luas.