Scope 3 Category 7: How to Calculate Employee Commuting Emissions

Why Commuting Is a Scope 3 Category Most SMEs Ignore

Scope 3 Category 7 — employee commuting — is one of the five categories the GHG Protocol flags as most likely to be material for service sector companies, yet it is the category most often skipped in supplier questionnaire responses. The reason is usually "we do not have the data." This guide shows you how to get the data in under an hour and produce a defensible estimate.

What Category 7 Covers

Category 7 covers greenhouse gas emissions associated with the transportation of employees between their homes and their regular workplaces during a reporting year. It includes:

• Commuting by car (petrol, diesel, hybrid, electric)
• Commuting by public transport (bus, metro, national rail)
• Commuting by cycling or walking (zero direct emissions)
• Remote working days (typically excluded — no commute occurs)

It does not include business travel (Category 6) or employee home office energy use (not currently a GHG Protocol category, though increasingly discussed).

The Three Data Collection Methods

Method 1 — Employee survey (most accurate) Send a short survey asking each employee: mode of transport, single-direction distance in km, and average days commuting per week. Most employees can answer this in 2 minutes. Response rate above 80% gives a reliable estimate.

Method 2 — Average distance assumption (practical) If a survey is not feasible, use the national average one-way commute distance and assume all employees commute by average car. For the UK, the average one-way commute is approximately 15 km (ONS 2023). For Germany it is approximately 17 km (Statistisches Bundesamt).

Method 3 — Office postcode distribution (for larger teams) Map employee home postcodes against office postcode to estimate distance distributions. Useful when payroll data includes postcode but an individual survey is not practical.

DEFRA 2023 Commuting Emission Factors

DeCarbonOPS uses the average car factor (0.170 kgCO2e/km) as the default for commuting when mode is not specified.

Worked Example — 15 Employees, Mixed Commute

Company: IT consultancy, London, 15 employees Survey results: 10 employees drive (avg 22 km round trip), 4 employees use national rail (avg 34 km round trip), 1 cycles

Calculation: - Car: 10 employees × 22 km × 220 working days × 0.170 kgCO2e/km = 8,228 kgCO2e - Rail: 4 employees × 34 km × 220 days × 0.041 kgCO2e/km = 1,227 kgCO2e - Cycling: 0 - Total Category 7: 9,455 kgCO2e = 9.5 tCO2e

As a share of total emissions, for a typical office company this would represent 20–35% of Scope 3.

Handling Remote Working

For employees working from home full or part time, the GHG Protocol recommends reducing commuting emissions proportionally. If an employee works from home 2 days per week, they commute 3 days, so use 3/5 of their annual days (132 days instead of 220).

A simpler approach accepted by most questionnaire platforms: apply a remote working adjustment factor to the full workforce. If 40% of your workforce is fully remote and 30% is hybrid (3 days in office), you can calculate a blended factor.

How DeCarbonOPS Calculates Category 7

In the DeCarbonOPS calculator: - Commute km/day (round trip) — enter the average daily round-trip commuting distance per employee - Employees — enter your average headcount for the reporting year - The calculator uses 220 working days and the DEFRA 2023 average car factor (0.170 kgCO2e/km)

If your workforce uses predominantly public transport or cycling, your actual emissions will be lower — note this in the methodology section of your questionnaire response.

Reporting Category 7 on Supplier Questionnaires

Include the following in your questionnaire response:

> "Scope 3 Category 7 (employee commuting): [X] tCO2e. Calculated using GHG Protocol Corporate Standard methodology. [N] employees, average round-trip commuting distance [X] km/day, 220 working days. Emission factor: DEFRA 2023 average car 0.170 kgCO2e/km. [Remote working adjustment applied / not applied]."

A DeCarbonOPS Carbon Passport includes Category 7 automatically and provides a permanent verification URL for the methodology.