Everything you need to know about ACEL


Everything you need to know about ACEL

ACEL© stands for Average Commuter Emissions Level. It is the only standardised methodology for benchmarking and comparing commuter emissions. This rating system empowers employers and communities to understand, benchmark and improve their commuting emissions.

What are the benefits of using ACEL?

What can be measured, can be managed. As the only standardised measure of commuter emissions, ACEL provides you a means to understand the size and impact of your workforce’s commute, part of Scope 3 requirements.

This insight allows you to take action to reduce your organisation’s effect on the environment. ACEL will enable your sustainability team to:

Set targets

Target setting can only be as effective as the validity of the method you’re using to measure them. Without a standardised measure, it’s impossible to know how your organisation is performing. Understanding the size and nature of your commuter emissions empowers you to set ambitious but achievable targets on your Zero Carbon Commuting journey.


You can use ACEL to measure the impact of your mobility initiatives. Set a benchmark by running a travel survey before your projects launch. Run another one after to measure how effective your changes have been. For example, if installing bike parking facilitates sees an uplift in employees biking to work, your ACEL will reduce. The lower the score, the more effective you have been in reducing your commuter emissions.

ACEL can also be used as a marker to compare against other organisations. This can invite collaboration and knowledge sharing on emissions reduction tactics. You can also compare your ACEL against local and national averages across the UK. You can see a full summary of each region on our ACEL Map.

You can also compare your ACEL against local and national averages across the UK. You can see a full summary of each region on our ACEL Map.

Implement change

ACEL provides a clear understanding of your emissions data allowing you to identify opportunities to reduce commuter emissions in both the long and short term. For example, calculating your ACEL enables you to quickly identify modes of travel that emit the highest levels of CO2e. This allows you to implement quick win strategies to encourage employees to make greener travel choices, such as incentivising active travel, adapting your infrastructure or partnering with third party travel schemes.

Measure your progress

Target setting is only valuable if you know when you’ve achieved success. ACEL’s numerical value is quick to calculate and easy to understand. Inputting the results of each travel survey allows you to benchmark your progress to measure and track emissions over time. Importantly, this allows you to evaluate when sustainability targets have been met.

How is ACEL calculated?

ACEL is based on a standard set of UK Government assumptions that are applied to your organisation’s travel survey results.

ACEL = Total commuting emissions / the number of workers

Average emissions per km assumptions

The data used to determine the average emissions for each mode per km of travel is sourced from the UK Government’s GHG (Green House Gas) conversion factors. This includes ratings for;

The average car, average lift-share (average car with 2 occupants), average vanpool (average van with 6 occupants), average motorbike, average taxi, average national rail, average light rail, average local bus and average domestic flight.

Park and ride is assumed to equate to the same emissions as an average car. This is in line with research showing park and ride facilities, while reducing inner city congestion, does not reduce car miles travelled.

Average distance commuted assumptions

The data used to determine the average distance commuted by each mode of travel is sourced from National Travel Survey. The survey collects information on how, why, when and where people travel, as well as other factors affecting travel (e.g. car availability and driving licence holding).

This is the UK’s primary source of data on personal travel patterns and is used to inform the development of Government transport policy. In the context of ACEL, data used to determine the average distance commuted by each mode of travel and commute frequency. On this basis, ACEL assumes the average commuter makes 182 return commuting trips per year.

Why is ACEL based on assumptions?

As per the use of GHG conversion factors, using averages to calculate ‘average’ commuter emissions is beneficial in a number of ways. Firstly, there are too many variables in an individual commute to capture data effectively. For example, a travel survey calculating an individual’s CO2e from a car-based commute would have to ask; fuel type, engine size, age of the vehicle, distance travelled, route taken, number of occupants and frequency of trip.

Using averages enables you to capture data using a lightweight question; ‘How do you travel to work?’. Simple, quick and direct questions require less stakeholder engagement allowing you to capture data from the largest possible sample of your workforce.

ACEL assumptions are updated annually in line with the Government’s travel and emissions data. This ensures ACEL accounts for changes in the mobility landscape, including the year-on-year emissions efficiencies of the ‘average car’.

With the increased adoption of electric vehicles and greener fuel alternatives, the average car’s emissions are reducing. This fall will be reflected in your organisation’s ACEL because the conversions factors are informed by the standardised average measures of the UK Government. This ensures it’s a fair benchmarking system for comparison over time, allowing you to effectively measure your progress.

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