Data Communications: Costs and Feasibility

OpenFare is now Universal Ticket Agent (UniTiAg). Please refer to that site for up-to-date information about UniTiAg business architecture and capabilities.

Let’s see whether it is possible to proactively synchronize open loop accounts and prepaid fare balances with each and every moveable validator (bus, streetcar, etc.) in the system.

When I first modelled this in 2012, and later, obtained U.S. patent 8,954,344 (which is now dropped), it was about data broadcast. 10 years ago, data broadcast was the only feasible way to proactively synchronize wireless validators with the central host of the transit agency, even for a mid-range public transit agencies.

Now, due to decreased cellular wireless data costs and increased data download speeds, data broadcast is not necessary even for large transit agencies.

The calculations summary is presented in the table below.

Transit System Scale Small *) Medium **) Large ***)
Number of patrons (mill.) 0.17 1.8 21
Max number of vehicles with validators en route 1,125 2,000 7,500
Average number of taps/sec in peak period 42 540 8,800
Validator storage (Mbytes) 60 600 7,000
Peak data download speed (Mbit/sec) 0.015 0.28 6.9
Annual cellular data cost (thousand $/year) 7.5 170 10,000
For comparison, cellular data cost as share of revenue 0.004% 0.005% 0.016% 
Peak validator download bandwidth measured in HDTV channels Close to 0 0.02 0.43

*) e.g.  Calgary, Canada

**) e.g. TTC, Toronto, Canada

***) Transport for London, UK

Today, (2022) when a cellular plan for 20 GBytes per month can cost around $50/month or less, and LTE download speed is several megabits per sec, synchronizing validators data with the central host’s database does not seem to be an issue, even during the peak periods. The patrons move slow between transfers, and synchronization lag of several minutes can be acceptable.

The model assumes 20% share of credit card accounts plus debit card accounts with high fare balance.  Those accounts can be synchronized with significantly slower pace or not synchronized at all. The daily caps schemes adopted by classic account-based fare systems work fine with them. If the share of trustworthy patrons is higher, the load on the cellular data can be lower.

However, for large transit systems, like Transport for London, UK, using data broadcast channels may be cheaper in long-term.

Those who are interested in smaller scale implementation, can skip reading the rest of this page.

Data Broadcast

Here is the data that can be broadcast to validators in one-to-many sessions (forget about costly Wi-Fi hubs and idling buses in depots while downloading files):

  • Transit system topology data such as stops, transit line configurations, transfer points, routes, and timetables
  • Fare tariffs, discount parameters, loyalty policy parameters, etc.
  • Validator software such as executable codes, voice messages, and display screens graphics
  • Negative card lists which classic open loop systems and closed loop systems use
  • Action and download lists which closed loop systems use
  • And, of course, fresh up-to-date ridership and payment data which OpenFare uses

When we are talking on the phone or streaming YouTube or Netflix we are receiving data that is intended to us specifically. We can ask a person who talks to us on the phone to stop, or we can make a pause or replay a movie. It is convenient, to receive information in this way at the time we want, and with the pace we want but it is more expensive because the signal is received in a one-to-one communication session. 30 min of HDTV movie can exhaust our monthly wireless data plan.

Broadcast means that the sender sends the signal only once, and many receivers listen for the signal, all at the same time, with the same pace. The cost of data broadcast is lesser because recipients share the telecom resource. Two or eight thousand validators installed on your buses and streetcars could share the same broadcast channel.

Data broadcasting technologies are known for decades but not all of them are good for our purposes. Let us take a look at the technologies we can use:

Satellite TV

Satellite High Definition Television (HDTV) broadcast is more than enough for our goals.  Renting one HDTV satellite channel for updating this data could cater for data broadcasting purposes of dozens transit agencies. The cost of this channel is less than the cost of Internet-based Wi-Fi depot infrastructure.

The issue with the HDTV-like satellite-based solution would be a cost of receiving equipment. Basically, you would have to equip each of your vehicles with a receiving satellite antenna plate. In some cases this can be reasonable. Some transit agencies do this anyway, for example, to provide their patrons with on-board Wi-Fi.

City TV Tower

Surprisingly, despite all cable services we have these days. many old TV towers are still functional and transmit several HDTV channels. The cost of receiving equipment is relatively low. As to the broadcast cost, most likely, it is the city who pays for it.

Digital Satellite Radio

An example of digital satellite radio could be XM Radio, well known in North America. Many North American cars have built-in XM Radio sets. XM Radio broadcasts hundreds radio channels using digital data technology. Less than dozen channels can cover the needs of one transit agency.

Cellular Broadcast

This is an emerging technology designed to address the needs of cellular phone owners wishing to watch movies on the cellular devices in the places without Wi-Fi. Cellular data broadcast is underused but known technology. You can read more here.