Driving cycle

Driving cycles are produced by different countries and organizations to assess the performance of vehicles in various ways, for example, fuel consumption, electric vehicle autonomy and polluting emissions.

Fuel consumption and emission tests are performed on chassis dynamometers. Tailpipe emissions are collected and measured to indicate the performance of the vehicle.

Another use for driving cycles is in vehicle simulations. For example, they are used in propulsion system simulations to predict performance of internal combustion engines, transmissions, electric drive systems, batteries, fuel cell systems, and similar components.

Some driving cycles are derived theoretically, as in the European Union, whereas others are direct measurements of a representative driving pattern.

There are two types of driving cycles:

1. Transient driving cycles involve many changes, representing the constant speed changes typical of on-road driving.
2. Modal driving cycles involve protracted periods at constant speeds.

The American FTP-75, and the unofficial European Hyzem driving cycles are transient, whereas the Japanese 10-15 Mode and JC08 cycles are modal cycles.

Some highly stylized modal driving cycles such as the European NEDC were designed to fit a particular requirement, but bear little relation to real world driving patterns. On the contrary, the current Worldwide harmonized Light vehicles Test Procedure (WLTP) strives to mimic real world driving behavior. The most common driving cycles are the WLTP, NEDC, SORDS and the FTP-75, the latter corresponding to urban driving conditions solely.

Driving cycle design is the core technology for these standard cycles. Optimization and Markov chains are employed to design a driving cycle.

Drive cycle recognition applies to Hybrid Electric Vehicle.

History

1960s

At the end of the 1960s, increased use of automobile vehicles led to the first regulations on limiting emissions. They first showed up in Germany and then in France, which led to the common Directive 70/220/EEC in March 1970:

• On 18 October 1968 was published, a 14 October 1968 regulation amended the Straßenverkehrs-Zulassungs-Ordnung in Germany with provisions on measures to be taken against air pollution by positive-ignition engines of motor vehicles, to enter into force on 1 October 1970;
• On 17 May 1969 was published in the Journal officiel a 31 March 1969 regulation on the "Composition of exhaust gases emitted from petrol engines of motor vehicles", applicable from 1971 or 1972.

This led to a risk to have different national regulation in different member states of the European Economic Community (EEC). To avoid this and to protect the common market, all member states adopts the same requirements, either in addition to or in place of their existing rules, in order to allow the EEC-type approval procedure, defined by Council Directive in 1970.

1970s

On 1 August 1970, United Nations Regulation No. 15. was registered by the United Nations Economic Commission for Europe (UN-ECE), for vehicles equipped with a positive-ignition engine or with a compression-ignition engine with regard to the emission of gaseous pollutants by the engine—a method of measuring the power of positive-ignition engines and a method of measuring the fuel consumption of vehicles. This UN-ECE regulation number 15 had three kind of tests performed with octane 99:

• Operating cycle used for TYPE-I TEST, up to 50 km/h speed in third gear and up to 1.04 meter per second squared acceleration
• TYPE-II TEST: Carbon-monoxide emission test at idling speed
• TYPE-III TEST: Verifying emissions of crank-case gases

In 1978, an Energy Tax Act mandated new testing in order to determine the rate of the guzzler tax that applies for the sales of new cars. This testing, the EPA Federal Test Procedure, commonly known as FTP-75 for the city driving cycle, is a series of tests defined by the US Environmental Protection Agency (EPA) to measure tailpipe emissions and fuel economy of passenger cars (excluding light trucks and heavy-duty vehicles).

In 1983, in the European Union, directive 83/351/EEC amended directive 70/220/EEC against air pollution by gases from positive-ignition engines of motor vehicles, in conformity with ECE Regulation No. 15/04.

1980s, NEDC

In the 1980s, the old NEDC as European homologation lab-bench procedure was established to simulate urban driving condition of a passenger car.

In 1988, in the EEC, Directive 88/76/EEC, change law to rules more stringent than ECE Regulation 15/04.

1990s

In 1992 the NEDC was updated to include also a non-urban path (characterized by medium to high speeds). In 1997 the CO₂ emission figure have been added, too.

The structure of the NEDC is characterized by an average speed of 34 km/h, the accelerations are smooth, stops are few and prolonged and top speed is 120 km/h.

In 1996, in the USA, the EPA revised the vehicle certification test, to introduce new driving conditions including aggressive driving behavior, high acceleration rates or air conditioners' operation: The new test introduces:

• speeds of 80 mph (129 km/h) instead of 57 mph (92 km/h).
• control of emissions during aggressive accelerations
• effect of air conditioners on nitrogen oxide

2000s

In 2007, the EPA added three new Supplemental Federal Test Procedure (SFTP) tests that combine the current city and highway cycles to reflect real world fuel economy more accurately,. Estimates are available for vehicles back to the 1985 model year.

In 2008, the US procedure has been updated and includes four tests: city driving (the FTP-75 proper), highway driving (HWFET), aggressive driving (SFTP US06), and optional air conditioning test (SFTP SC03).

2010s

Nowadays, the NEDC cycle has become outdated, since it is not representative of the modern driving styles, since nowadays the distances and road variety a mean car has to face have changed.

From 1 September 2019 all the light duty vehicles that are to be registered in the EU countries (but also in Switzerland, Norway, Iceland and Turkey) must comply with the WLTP standards, part of the Global regulations: In the European Union, including UK, the WLTP replaces the NEDC.

2020s, CATC

On 2019-10-18, the China automotive test cycles (CATC) are released (GB/T 38146). CATC are concluded from a research covering over 17 vehicle models, 2.5 million data inputs, 700 thousand car owners and 31 provinces in China. On 2020-05-01 CATC are into effect.