Friday, June 17, 2011

Passenger communication on a fragile network

On a rail network prone to disruption due to track faults, signal failures, loss of power, train faults and level crossing accidents, communication with passengers is critical.

This morning's power failure between Frankston and Carrum stations (due to a truck running into a power pole) caused widespread service disruptions during the network's busiest period. It also sorely tested the capabilities of each communication system available.

Passengers at unattended stations (ie the majority) have the following facilities:

1.Automated PA announcements of next train

2.Manual PA announcements (from control station)

3.Green button

4.Red button (intended for emergencies)

5.SMS alerts (sent by train control)

The strengths and limitations of each will now be discussed

1.Automated PA announcements

These announcements are broadcast via horn speakers located on light poles along the platform. Volume varies and messages are sometimes inaudible at some points along the platform (even though it's desirable to spread passenges along it to speed boarding). This is especially the case during the morning peak at stations near busy highways where peak road traffic drowns out announcements. In contrast volume is well above ambient noise at night - even to the point where local residents complain. Of course these automated announcements presuppose trains are operating so are of limited usefulness when service is suspended (unless set to disruption mode at a control desk).

2.Manual PA announcements

Manual PA announcements can be the best means of communicating to passengers at remote unstaffed stations, especially when circumstances change at short notice. These use the same speakers as the automated announcements but are far more useful in the event of disruption. This effectiveness is enhanced because control desks are able to make these specific to a particular station or for a large section of line (most useful for large-scale disruptions as on Friday).

Like automated announcements, intelligibility may be low in noisy station environments (as was the case today). Different staff have different speaking voices and levels, further affecting clarity. Control desk staff are not studio technicians and have no access to level and tone adjustments – and even if they did there’s no staff at unstaffed stations to check. While not a panacea, audio compression may help as it reduces volume changes between different voices and thus improves readability.

Frequency of announcement is equally critical, especially during peak periods where hundreds of passengers per minute are entering stations along the line. Ideally these should be every two minutes. Operational circumstances vary and it is difficult to assure quality. However intervals of up to eight minutes between manual announcements are not acceptable, especially if not all are intelligible and other communication methods are not working.

3.Green button (or ‘PRIDE’)

This is the chief means of real-time information at stations without ‘next train’ visual displays. Passengers press the green button and hear next train announcements, including ‘minutes to’. This works most of the time, but, during disruptions the ‘minutes to’ announcement may be omitted. This is most important in helping passengers decide whether they should wait or seek other transport. The system may also sometimes ‘ring out’ and not provide any annoucement. This is understood to be most likely when too many passengers at too many stations are pressing the button at once (a particular risk at unstaffed stations that haven’t seen a train for a while).

4. Red button

This is intended for emergency use only and allows two-way contact with the nearest control station. However passengers sometimes press it, either accidentally, maliciously or to enquire about delayed or disrupted services when announcements have been infrequent or inaudible. Sometimes this reminds the control desk that another PA announcement is overdue and one is given soon after.

5. Text alerts

Mobile phone text alerts are the latest way of informing passengers of service disruptions. They originate from the CBD-based train control, ie a different source to local manual announcements. Passengers can customise required information to their line and travel times and information, if given sufficiently in advance, is provided before the passenger reaches the station. Alerts are often received after the time has passed for passengers to do anything about it - especially where trains are altered to bypass the City Loop or major disruptions cause high message volumes and slow sending. Increasingly important, as more get mobile internet, will be website alerts, again issued from Metrol.


Each information system has its strenghts and limitations. Performance, such as clarity, accuracy and timeliness, often suffers when it is most needed, ie during service disruptions. Substantial improvements in all methods are desirable but it would seem to me that the humble manual PA announcement made locally (or to a group of stations on a line) offers the greatest potential to be cheaply improved in both quality and quantity.


Daniel said...

There's also Twitter, which to a limited extent is "pushed" to followers, provided they are monitoring it. Note the use of the Twitter #MetroTrains hashtag in SMS alerts recently (including your example).

gxh said...

Another form of communication is the multi-line "next train" display, such as at the Malvern to Hawksburn group of stations (and probably elsewhere but not of course at every station). This can be programmed to show (typically on the bottom line) a message about disruptions. This regularly occurs and is quite effective.