# Waiting for 'real-time' buses

Sir, – Your correspondent, Donal Lyons (June 20th) clearly spent a miserable hour waiting for his Number 14 bus on June 12th. He relied on information from our Real Time Passenger Information signs to tell him when his bus was due. Something evidently happened that day with the Number 14 bus service and also with the information the 14 buses were passing to the Real Time system.

I will follow up with Mr Lyons directly regarding details of what time on June 12th he was waiting on Nassau Street, and we will then check why no bus arrived over the particular hour he was waiting. We will use that information to remedy the problem.

System accuracy is very important to us; we constantly test the signs, survey them and update them, to maximise accuracy. Our latest survey, in April, looked at data from 15 specific sites around Dublin covering 940 buses. The average accuracy was 93 per cent; this compares very well with bus-based real time passenger information systems internationally, which aim for 90 per cent accuracy. Bus-based real time information systems, in any city in the world, are complex due to traffic congestion, communications and operational issues. – Yours, etc,

GERRY MURPHY,

Chief Executive,

National Transport Authority,

Harcourt Lane, Dublin 2

Sir, – I’m afraid the information supplied by Donal Lyons (June 20th) is just as inaccurate as the information given on the “real time” bus-stop about which he complains.

He tells of his experience that the noticeboard indicated his bus was due in four minutes, later changing to three before immediately showing five, followed by other changes. He observes the bus arrives “100-150 per cent later than initially predicted”. This is mathematically impossible. The shortest delay, the lowest point of his range, taken from the time the notice indicated five minutes would mean the bus arrived 10 minutes after that point. However immediately before five minutes was displayed the information given was three minutes, making a delay from that point greater than 233 per cent. While the data he gives is clearly incorrect he has given me the idea of a great way to pass the time by playing with simple maths as I await the arrival of my bus. – Yours, etc,

DECLAN FITZPATRICK,

Long Lane, Dublin 8.