The Driving Cycle: What You Need to Know

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Different Driving Cycles

Different Driving Cycles by Science Direct

Do you know what the driving cycle is? Probably yes, but perhaps you want to know more about it. When it comes to driving, there's a lot more to it than just putting your foot on the gas and steering. To drive safely and efficiently, you need to be aware of the different driving cycle phases as well as their duration and how many miles they cover.

Each phase has its own set of rules and procedures that you need to follow to stay safe on the road. So, what are these phases, and what do they involve?

What is Driving Cycle?

The term "driving cycle" refers to a test that measures vehicle speed over time. It is used to evaluate a car's fuel consumption and pollutants emissions in a standardized way to compare similar vehicles. The driving cycle is carried out on a chassis dynamometer, where tailpipes automobile emissions are collected and analyzed to assess emission.

History

In 1970, the Economic Commission of Europe (ECE) vehicle regulations introduced the first-ever driving cycle test, the ECE-15, also known as Urban Driving Cycle (UDC). In 1990, the Environmental protection Agency (EPA) added the Extra-Urban Driving Cycle (EUDC) to the Urban Driving Cycle (UDC). Before 1990, fuel consumption and two constant velocities of 90 and 120 km/hr were included in the UDC.

The above-said speeds and velocities were designed to match the fuel consumption of specific vehicles; however, because real-world driving differs, these figures may not accurately reflect actual fuel consumption.

Environmental groups have criticized this for not accurately reflecting how much pollution an average driver would create. Therefore, another type called "Worldwide Harmonized Light Vehicle Test Procedure" (WLTP)  was introduced because they believe it is more accurate than the EUDC.

Types of Driving Cycles

Modal Driving Cycles

Also defined as the European Driving Cycle or the Japanese 10-15 Mode Cycle, the Modal Driving Cycle is a compilation of straight acceleration and constant speed periods. This isn't an actual drive but rather shows how fuel consumption will be expected over a real-life driving situation.

In Europe and some other countries, the Modal driving cycle is used as a reference cycle for approving vehicles standard. It consists of an urban driving cycle (UDC) and an extra-urban section called EUDC. 

This cycle requires repeating the process four times for three tests. At the same time, the Japanese 10-15 mode cycle is being used for emissions and fuel efficiency testing in Japan. 

This test includes idle, acceleration, cruising, and deceleration cycles similar to those found on the Urban and highway driving cycles. As mentioned earlier, despite modal cycles having significant advantages for emissions and fuel economy testing, experts have criticized them for their unrealistic driving conditions. Because of this, transient driving cycles were introduced.

Transient Driving Cycles

Developed by the US EPA, the Transient Driving Cycles was adopted as a federally mandated test procedure for light-duty vehicles such as cars, minivans, and sport utility vehicles. This test procedure lasts for 28 minutes and covers 11.92 miles (19 km). An example of this is the Artemis Driving Cycle (FTP 75).

The Artemis Driving Cycle tests how the vehicle performs in actual world road conditions. This type of driving simulates how a car will drive over an average trip, including many stop-and-go situations as well as acceleration periods.

Artemis cycles are not used to certify pollution or fuel consumption; however, vehicle manufacturers employ this cycle to understand real driving situations and evaluate their cars' actual performance. This comprises three parts: city, suburban, and highway.

Urban Driving Cycle

The Urban Driving Cycle consists of two tours through town with low-speed limits, multiple stops and starts, and the most constant speed or slow acceleration between speeds below 50 km/h (31 mph).

Sub-Urban Driving Cycle

This driving cycle is carried out by a dynamometer to test heavy-duty vehicles. This monitors how the car performs during long-distance highway drives on open roads without any obstacles like traffic lights along the way.

Highway Driving Cycle

The Highway Driving Cycle is a single tour covering the entire range of speeds, from 0 to 100 mph. The test vehicle starts from a stop and accelerates to 60 mph. It then cruises at 60 mph for a period before coming to a complete stop. After reaching a stop, it accelerates back up to 60 mph and repeats the pattern.

Other Types of Driving Cycle

Since driving cycles are a crucial element for measuring fuel consumption and emissions, the EPA added another type of driving cycle to form the Diagnostic Test Mode (DTM). This cycle is called the Harmonized Driving Cycle.

The Harmonized Driving Cycle is carried out on a chassis dynamometer like the previous cycles. It allows the proper assessment of pollutants, emissions, fuel economy, and electric range in light-duty vehicles. This was designed to replace the NEDC cycle by 2013-2014 with the help of European, Japanese and Indian experts.

The test procedure is divided into three cycles depending on the tested car's power-to-mass ratio. This PMR, which equals the rated power in W divided by curb weight in kg, is determined using a formula. To illustrate how the test procedure process formula works we provided a sample table below:

Power to mass ratio

Equivalent

Class 3

PMR ≥ 34

If Vmax < 135 km/h, the Extra High-speed part is replaced with Low-speed part

Class 2

22< PMR < 34

If Vmax < 90 km/h, the High-speed part is replaced with Low-speed part

Class 1

PMR ≤ 22

If Vmax < 70 km/h, the Medium-speed part is replaced with Low-speed part

Class 3

Considered as the highest power-to-mass ratio, this class represents all the types of vehicles driven in Europe and Japan. It comprises four-speed zones: urban driving, one sub-urban driving, one extra-urban driving, and a highway zone.

Class 2

This represents the types of vehicles in India and low-power cars in Japan and Europe. This cycle is divided into two-speed zones: slow and medium. 

Class 1

Since this type has the lowest power-to-mass ratio, this class is made up of low and medium-speed zones, which represents the types of vehicles driven in India. 

Why is the Driving Cycle important?

Driving cycles play an important role in vehicle evaluation and standards. They are also crucial in monitoring the environmental impact of vehicles because they can assess fuel consumption and pollutant emissions. Aside from those, there are several benefits, you can get in the driving cycle including:

  • It lessens the chances of you being in an accident.
  • You can have a better fuel economy.
  • It improves the lifespan of your car's engine.
  • It analyzes the battery state and energy consumption to help you save on charging time.
  • It assesses the vehicle model before using it for various purposes, such as how well it handles slippery            conditions or how quickly its engine warms up so that you can decide whether or not this type of vehicle        is right for your needs.
  • It checks the vehicle's performance, such as how fast it accelerates from 0km/h (0mph) to 100km/h                 (62mph), how much fuel consumption per km is used, how well brakes work, etc.
  • It assesses how much noise a model emits when running at different speeds so that you can decide                whether this type of vehicle meets your needs for comfort level while traveling with others in close                  quarters (such as inside an apartment building.

How long does it take to complete the Driving Cycle?

On average, it takes 30 to 60 minutes to complete the driving cycle. However, it may vary depending on the type of driving being done, how long it takes to reach the required speed limit, and how many stops are made.

How many miles does the Driving Cycle cover?

The driving cycle covers about 50 to 100 miles total. As you drive, your car's computer performs different test sections such as idle, acceleration, cruising, and deceleration. The computer will monitor how the car's emissions system performs during each section.

Once you have completed the drive cycle, your car's computer will generate a report showing how well the emissions system works. The mechanic will then use the report if your car needs any repairs.

How do Driving Cycles help in Emission Tests?

All cars produced in the early 1980s and later have some onboard diagnostic computer, and the OBD II system has been standard on all light-duty vehicles. The vehicle computer monitors a variety of emissions-related factors and alarms you if there is something wrong with how your car is running.

If the vehicle's performance falls outside the permissible limits, the computer illuminates the "Check Engine" light. You cannot pass the emission test when the check engine light is activated, and you'll be required to do the driving cycle to pass the test. 

Many situations have shown that doing so will put your vehicle in "ready" mode. However, this will not solve your car's problem or improve its performance.

How Do You Perform the Driving Cycle?

Suppose you are going for a smog test, and you need to make sure you're going to pass the test. In that case, you must do the driving cycle. This will run your vehicle onboard diagnostics and detect potential malfunctions in your vehicle's emission system. The driving cycle is not just one test; it combines different tests, which include: 

  • Accelerate 
  • Decelerate
  • Steer 
  • Change Gear
  • Brake
  • Idle/Neutral

Important: You'll need to complete a drive cycle to pass the emission test. For better results, it's best to run at least two cycles as many cars won't pass or fail on the first attempt. To perform these tests:

Step-by-Step Guide

  1. Before you start the test, check all your car accessories. Make sure that all are OFF. These include your AC, radio, etc.
  2. Make sure that your "Check Engine" light is OFF.
  3. Inspect your fuel tank. The fuel level should be between ¼ and ¾ full.
  4. Ensure that the engine temperature is cold or below 100 degrees.
  5. If your think you're ready to drive, you can now start your engine and start driving.
  6. Accelerate to 30 mph with constant, moderate acceleration. Hold for two to three minutes at a steady speed.
  7. Maintain a constant speed of 55 mph for 3 minutes.
  8. Decelerate and lift your foot from the accelerator pedal. Do not shift, brake, or use the clutch. It is critical to let the car coast down to 20 mph gradually. 
  9. Accelerate at 3/4 throttle until you reach 55-60 mph. This will run the same diagnostics that step 3 did.
  10. Maintain a constant speed of 55 mph for five minutes.
  11. Decelerate. Again, do not engage the clutch, brakes, or alter gears.
  12. The drive cycle is complete.

Important: To get an accurate reading, each driving cycle is repeated three times and then averaged together. This gives you a good indication of how the car will behave when you're driving.

Driving Cycle FAQs

1. How do I know if my driving cycle is complete?

The Pulse-code Modulation (PCM) will tell you if the driving cycle is complete. The Check Engine Light (CEL) will illuminate for a few seconds, then turn off. If the CEL does not illuminate, or it illuminates and stays on, this means that your vehicle has failed emissions testing.

2. What happens if I don't complete the driving cycle?

If you do not complete the drive cycle, your vehicle will fail emissions testing. You will have to go back again and repeat the entire process. 

Suppose this is a new car that has never been registered or driven before. In that case, it may be necessary to drive at least 100 miles and allow idle periods for all of the sensors and monitors to become active before beginning the drive cycle.

3. Where should the driving cycle be completed?

You should do the driving cycle on a closed track or course. This will help ensure that you complete the entire cycle without interruption. However, if it is not possible, you can complete it on public roads. Just obey all traffic laws and avoid congested areas whenever possible.

4. Who will do the driving cycle process?

Someone should do the driving cycle with some experience. This will help ensure that the process is completed correctly so you can get your vehicle inspected and registered on time.

The person doing the drive cycle needs to know how to operate a manual transmission vehicle, if applicable in your case.

5. Does the driving cycle fix my car issue?

The driving cycle is not a be-all and end-all fix for your car's emissions issue. It will, however, help get your vehicle inspected and registered so you can drive it legally. If your car still does not pass the emissions test after completing the cycle, you should take it to a professional mechanic for diagnosis and repair.

Conclusion

The driving cycle is an essential part of emissions testing as it helps ensure that your car meets all the environmental regulations. It's also a great way to guarantee that your vehicle runs smoothly and efficiently. Make sure you complete the cycle regularly to keep your vehicle in top condition.