CNG trucks and buses: UN R110 cylinder types, 20 MPa filling and makers' models

A CNG truck or bus runs on natural gas that it carries as a compressed gas in high-pressure cylinders on the vehicle. UN Regulation No 110 covers the specific components of category M and N vehicles that use compressed natural gas (CNG) or liquefied natural gas (LNG) in their propulsion system, and the installation of those components in the vehicle. In the text the European Union published in its Official Journal on 30 June 2015, the Regulation sorts gas cylinders into four types, CNG-1 to CNG-4, bases them on a working pressure of 20 MPa settled at 15 °C with a maximum filling pressure of 26 MPa, and caps a cylinder’s service life at 20 years. The UN has amended the Regulation since; the most recent notifications are dated 24 June 2025 and include amendments binding from 12 June 2025. In the European Union, the Alternative Fuels Infrastructure Regulation (AFIR) sets the fuelling pressure and connector of CNG refuelling points, but no target for their number. Anadolu Isuzu, Gillig, Iveco Bus, MAN and Otokar describe CNG or natural gas buses on their own pages, and Iveco a CNG version of its Eurocargo truck.

Status as of 14 November 2026. Read on that day: UN Regulation No 110 in the text published in the Official Journal of the European Union, OJ L 166 of 30 June 2015, in English and in the German, Spanish, French, Italian and Polish versions, from the Publications Office of the European Union; the UN Treaty Collection’s status sheet for the Regulation and its depositary notification C.N.318.2025; Regulation (EU) 2023/1804 (AFIR) in its Official Journal text, whose Article 2(4), Article 17(6), Article 21(1) and Annex II points 4.1 and 4.2 read the same in its consolidated text of 8 January 2026; and the makers’ pages and documents named in the table below. The Official Journal publication of Regulation No 110 states that “Only the original UN/ECE texts have legal effect under international public law.”

Compressed natural gas on the vehicle

Regulation No 110 defines a “CNG system” as “an assembly of components (container(s) or cylinder(s), valves, flexible fuel lines, etc.) and connecting parts (rigid fuel lines, pipes fitting, etc.) fitted on motor vehicles using CNG in their propulsion system” (paragraph 4.10), and a container, or cylinder, as “any storage system used for compressed natural gas” (paragraph 4.12). Its Part I covers the approval of the components themselves and Part II the approval of a vehicle with regard to their installation; both apply to vehicles of categories M and N, the categories explained in vehicle categories M, N and O.

Paragraph 3 sorts the components by pressure and function. Class 0 covers “High pressure parts including tubes and fittings containing CNG at a pressure higher than 3 MPa and up to 26 MPa”; Class 1 covers medium-pressure parts, Class 2 low-pressure parts, Class 3 medium-pressure parts such as safety valves or parts protected by a safety valve, Class 4 parts at a pressure lower than 20 kPa, and Class 5 parts in contact with temperatures below -40 °C. The gas cylinders are Class 0 parts (Annex 3A, paragraph 1). These component classes are not the cylinder types described below.

The same Regulation covers liquefied natural gas, and on an LNG vehicle the parts “downstream from the vaporiser shall be considered as CNG components” (paragraph 4.11). The difference in energy density between liquefied and compressed gas, and LNG trucks themselves, are covered in LNG and bio-LNG trucks, which also quotes AFIR’s Article 2(4)(c), the provision that lists CNG and LNG among the “non-renewable alternative fuels and transitional fossil fuels”.

Four cylinder types: CNG-1 to CNG-4

Paragraph 4.13.1 and Annex 3A, the annex on high-pressure cylinders for the on-board storage of CNG, name four types of container. Annex 3A also says on what each type’s life rests.

The German and Polish versions of the 2015 text keep the designations CNG-1 to CNG-4; the Spanish, French and Italian versions write them GNC-1 to GNC-4. Makers’ documents do not always use either. MAN’s Lion’s City G page lists “Gas cylinders type 4”, Iveco Bus’s natural gas data sheet for the Crossway Line and Pop prints its CNG tank as “Class III” with a “Class IV” option, and Gillig’s CNG page speaks of “lightweight composite fuel cylinders”. In Regulation No 110, Class 0 to Class 5 are the classes into which paragraph 3 sorts components by pressure and function.

Pressure: 20 MPa settled, 26 MPa at filling

Regulation No 110 defines working pressure as “the maximum pressure to which a component is designed to be subjected to and which is the basis for determining the strength of the component under consideration”, and adds: “For CNG cylinder, the settled pressure of 20 MPa at a uniform temperature of 15 °C” (paragraph 4.4). Service pressure is “the settled pressure at a uniform gas temperature of 15 °C” (paragraph 4.2). Annex 3A is “based upon a working pressure for natural gas as a fuel of 20 MPa settled at 15 °C with a maximum filling pressure of 26 MPa”; other working pressures “can be accommodated by adjusting the pressure by the appropriate factor (ratio)”, so that in the annex’s own example a 25 MPa working pressure system multiplies the pressures by 1.25 (paragraph 1).

Paragraph 4.2 of the annex limits the cylinder pressure to a pressure that would settle to 20 MPa at a settled temperature of 15 °C, and to “26 MPa, immediately after filling, regardless of temperature”. The cylinders are designed to be filled to a settled pressure of 20 MPa, which the annex also writes as 200 bar, up to 1,000 times per year of service (paragraph 4.3), and for a settled gas temperature from -40 °C to 65 °C (paragraph 4.4.1). The refuelling side of the same figures is set in the EU by AFIR.

Service life, markings and the 48-month visual inspection

Under Annex 3A, “The service life of the cylinder shall be defined by the manufacturer and may vary with applications.” The definition of service life is based on filling the cylinder 1,000 times a year for a minimum of 15,000 fills, and “The maximum service life shall be 20 years” (paragraph 1). Paragraph 4.1.3 repeats the 20 years and says the service life is to be specified by the cylinder designer.

Paragraph 11 of the annex requires clear permanent markings on each cylinder, “not less than 6 mm high”. The mandatory ones begin with “CNG ONLY” and “DO NOT USE AFTER XX/XXXX”, where the figures give the month and year of expiry, and a footnote adds: “The expiry date shall not exceed the specified service life.” The other mandatory items include the manufacturer’s identification, a part number and a serial number unique to each cylinder, the working pressure and temperature, the ECE Regulation number with the cylinder type and certification registration number, and the pressure relief devices or valves qualified for use with the cylinder. The annex’s example of the mandatory markings includes the lines “20 MPa/15 °C” and “ECE R 110 CNG-2 (registration No …)”.

Paragraph 4.1.4 of the annex sets one interval: “Each cylinder shall be visually inspected at least every 48 months after the date of its entry into service on the vehicle (vehicle registration), and at the time of any reinstallation, for external damage and deterioration, including under the support straps.” The inspection “shall be performed by a competent agency approved or recognised by the Regulatory Authority, in accordance with the manufacturer’s specifications”.

The green CNG label on buses

Paragraph 18.1.8.1 requires vehicles of categories M2 and M3 equipped with a CNG system to be labelled as specified in Annex 6. The label goes on the front and rear of the vehicle and on the outside of the doors on the right-hand side of a left-hand-drive vehicle, or on the left-hand side of a right-hand-drive vehicle (paragraph 18.1.8.3). Annex 6, whose heading also names categories N2 and N3, describes a weather-resistant sticker with a green background, a white or white reflecting border and white or white reflecting letters, 110 to 150 mm wide and 80 to 110 mm high, with characters at least 25 mm high and 4 mm thick and the word “CNG” centred in the middle. Vehicles of the same categories with an LNG system carry a sticker of the same design with the word “LNG” (paragraph 18.1.8.2 and Annex 7).

Regulation No 110 after 2015

The 2015 Official Journal text incorporates “all valid text up to” Supplement 2 to the 01 series of amendments, which entered into force on 9 October 2014. The UN Treaty Collection gives 28 December 2000 as the date the Regulation entered into force, and its status sheet lists the Contracting Parties applying it, among them the European Union, Norway, the Russian Federation, Serbia, Switzerland, Türkiye, Ukraine and the United Kingdom. The sheet records amendment notifications in later years as well, the latest seven of them dated 24 June 2025.

One of those seven, C.N.318.2025, says that amendments communicated to the Contracting Parties by a notification of 12 December 2024 “are considered to be adopted and are binding upon all Contracting Parties applying the above United Nations Regulation as of 12 June 2025”. Their text is document ECE/TRANS/WP.29/2024/107, which the notification places on the website of the UN Economic Commission for Europe. That website could not be read on 14 November 2026, so the cylinder types, pressures, service life, markings, inspection interval and label above are those of the 2015 text; whether the later amendments changed any of them could not be checked.

AFIR: rules for CNG refuelling points, no target for their number

Regulation (EU) 2023/1804 on the deployment of alternative fuels infrastructure has applied since 13 April 2024 (Article 26). Article 21(1) says “The technical specifications set out in Annex II shall apply”, and point 4.1 of Annex II reads: “Refuelling points for compressed natural gas (CNG) for motor vehicles shall comply with a fuelling pressure (service pressure) of 20,0 MPa gauge (200 bar) at 15 °C. A maximum fuelling pressure of 26,0 MPa with ‘temperature compensation’ is permitted in accordance with standard EN ISO 16923:2018.” Point 4.2 ties the connector profile to Regulation No 110, “referring to parts I and II in standard EN ISO 14469:2017”.

The Regulation’s articles on road infrastructure set targets for recharging points (Articles 3 and 4) and for hydrogen refuelling (Article 6), and Article 8 deals with liquefied methane; none of them concerns CNG. CNG appears in Article 17(6), under which the Commission “shall make publicly available and regularly update information on the national targets and the objectives submitted by each Member State” regarding, among other things, “the number of publicly accessible refuelling points for CNG for motor vehicles” (point (g)). Recital 8 says that “liquefied petroleum gas (LPG) and compressed natural gas (CNG) vehicles, for which sufficient infrastructure network already exists across the Union are expected gradually to be replaced by zero-emission powertrains”. The heavy-duty recharging targets are set out in AFIR charging targets for trucks, the hydrogen targets in hydrogen refuelling for trucks in Europe and the liquefied methane article in LNG and bio-LNG trucks.

Makers’ CNG trucks and buses

The model pages with CNG or natural gas versions give more detail. For buses: the Isuzu Citiport, the BMC Procity, the Gillig Low Floor, the Iveco Crossway, Crossway LE, Streetway and Urbanway, the MAN Lion’s City and the Otokar Kent and Territo. For trucks: the Iveco Daily, Eurocargo, S-Way, Stralis and X-Way, the Mack Granite, the Peterbilt 537 and 548, the Renault Trucks D, the Scania G-series, P-series and L-series and the Volvo FE. Several of the engines are described under the FPT Cursor 9, FPT Tector 7, Cummins L9 and MAN E18.

Gross weights and passenger capacities of CNG city buses are listed in bus weight and seating capacity, and the other drivelines of city buses in city bus propulsion. The conditions for gas-powered vehicles on the Channel Tunnel freight shuttle are set out in trucks on ferries, trains and the Channel Tunnel, and the treatment of CNG vehicles in individual low-emission zones in low-emission zones for trucks and buses in Europe.

Biomethane as bio-CNG

AFIR lists “biomass fuels, including biogas” among its “renewable fuels” (Article 2(4)(b)), and its recital 5 ties the use of fossil gaseous or liquid fuels to “increasing blending with or replacement by renewable fuels such as bio-methane”. On the makers’ side, Iveco’s Eurocargo release of 15 November 2023 speaks of CNG vehicles “When they run on biomethane”, and Gillig’s CNG page names Renewable Natural Gas (RNG) as a fuel for its CNG buses. How the EU’s CO2 rules for new heavy vehicles treat biomethane, and the end of the German toll exemption for gas trucks, are set out in LNG and bio-LNG trucks; the gas qualities MAN gives for its city bus engine are listed under MAN E18.