SIRI and GTFS Realtime: frenemies?

The latest revision of the MMTIS Delegated Regulation has put a stronger emphasis on sharing real-time data publicly via National Access Points (NAP). It has also put forward SIRI as the European norm to use. However, some industry stakeholders have put their effort in GTFS Realtime. So, you might be wondering if the two data exchange formats are compatible and which one to use. We tell you all below, so read further!

First, let’s lay the groundwork

Before we dive into more technical discussions, here is what you need to know about SIRI and GTFS Realtime (also referred to as GTFS-RT).

📚SIRI

SIRI is a European norm:

• governed by CEN,
• that enables the exchange of all realtime (or dynamic) information describing the current status of a public transportation service,
• based on the reference conceptual data model Transmodel, which serves as both a dictionary and a grammar to SIRI,
• designed for passenger information, inter-system exchanges, and open data.

📗GTFS Realtime

GTFS Realtime is a standard:

• maintainted by MobilityData,
• that enables the exchange of realtime information describing the status of a transit service,
• designed for passenger information and open data.

Note: Norms and standards differ by their governance body. Only norms are governed by an official standardisation body such as ISO, CEN or a national standardisation body (e.g., ANSI in the USA, BSI for Great Britain, DNI for Germany, AFNOR for France).

Why two standards?

They do not come from the same continent and do not share the same vision, nor the same history.

Born on opposite sides of the world

SIRI and GTFS Realtime have different approaches to modelling.

• Born in Europe 🇪🇺, SIRI follows the spirit of: “I strive to build a consensus shared by all Member States and I must allow for the diversity of public transport to be represented”.
• Born in the USA 🇺🇸, GTFS-RT follows the spirit of: “I start by keeping things simple and grow as needs arise and/or transit evolves”.

Different visions and history

SIRI and GTFS do not share the same vision of public transport:

• 🚌🚕🚲🛴🚎🚄 SIRI (and Transmodel) covers all public transport (i.e., any advertised public transport service and available for use by the public, regardless of its mode of operation),
• 🚌🚕🚎🚄 GTFS Realtime covers public transport with conventional modes of operation (i.e., transit and flexible modes)

One has also to keep in mind that:

• 🚧🛠️🛗 SIRI was long pre-existing, it was actually the very first CEN standard to be used by most public transport services for their realtime data exchange between systems. For example,it provides different services such as Facility Monitoring for the current status of an equipment. It is also a stand-alone standard with feeds that do not necessarily need NeTEx to be understood.
• 🚧 GTFS Realtime was created later to complement GTFS and does not exist as a stand-alone standard.

For more details on the modes of operation of public transport covered by Transmodel: © CEN, TC278, WG3, SG4 (CC-BY-SA)

Learn more on Transmodel

Who is it for?

SIRI and GTFS Realtime were not designed for the same data consumers.

👩‍💻 SIRI was designed for various consumers of multimodal mobility data. Therefore, it allows different broadcasts of services depending on whether you:

• feed your own trip planner with richer real-time information,
• provide data to other IT systems (e.g., equipment management, fleet management, etc.),
• export open data required by national and European regulations,
• perform advanced statistics on your public transport offer (and in particular the link with OpRa).

📍 GTFS Realtime is designed for the most widely used trip planners (e.g., Google Maps, Transit App, Citymapper, etc.). Therefore, it only includes data that is essential for:

• describing the current status of a transit service,
• taking into account the minimum information required for passenger information.

And what about Ara SaaS?

Our product allows you to broadcast natively your data in both SIRI and GTFS Realtime to feed all your data consumers based on their preferences without added costs.
Our goal is to help you improve and enrich your multimodal mobility data without having to worry about their export format. We believe that your time is better spent taking the control of your mobility data.
Ara SaaS also allows you to broadcast your real-time services in open data in one click.
All of this thanks to:

• a SaaS product, that evolves without you having to pay more,
• a team of passionate experts, involved in standardisation work,
• an active listening to all your needs, so we can support you with your projects.

To learn how to publish your data in both SIRI and GTFS Realtime, read the next article.

How to broadcast my data in both SIRI and GTFS Realtime