How to calculate taxi and rideshare emissions

Taxi and rideshare trips are among the most frequently overlooked sources of business travel emissions — and one of the highest-impact intervention opportunities. For programmes where employees regularly take airport taxis, ride-hails to client offices or cabs between meetings, the aggregate footprint adds up. This guide explains how taxi and rideshare emissions are calculated and why getting this category right matters beyond the numbers alone.

Where taxis and rideshare fit in Scope 3 Category 6

Taxi, rideshare and private hire vehicle trips taken on behalf of the organisation sit in Scope 3 Category 6 — Business Travel. This includes airport transfers, point-to-point rides to client sites, and any hired vehicle journey where the employee is travelling for work. It does not include commuting (Category 7) or personal rideshare not expensed to the organisation.

In practice, taxi trips are often captured via expense systems rather than booking tools — which means data quality can be lower than for flights or rail. Some tools integrate with expense platforms to pull taxi spend data and convert it to distance-based emissions estimates where direct distance data is unavailable.

How taxi emissions are calculated

The calculation follows the same approach as other ground modes:

Method 1: Spend-based (most likely)

Where only expenditure data is available, a spend-based approach using EEIO factors is possible as a fallback, but is significantly less accurate than distance-based and not recommended for reporting where trip-level booking data can be sourced from a TMC or expense system.

Method 2: Distance-based (recommended default)

The activity data is the journey distance in kilometres. Where trip distance is not available from the booking system, it can be estimated from origin and destination postcodes. The emission factor is expressed in kg CO₂e per kilometre and varies by vehicle type. Most booking companies will specify vehicle type, so electric taxi usage can be measured.

DEFRA provides average taxi/cab factors:

Source: DEFRA 2025. Average taxi factor includes diesel and petrol cabs in the UK fleet mix. All emissions factors include WTT. For electric taxi, the Battery Electric vehicle factor (executive BEV) is used. For Large executive car/SUV, the Executive Unknown factor is used.

Method 3: Fuel-based

The most accurate calculation, but fuel data is often unavailable. If taxis and rideshare travel represents your most material travel emission category, you should try to use fuel data wherever available.

Why this matters: the last-mile intervention

Airport taxi transfers are not large in absolute terms per trip. But for programmes where hundreds of employees take taxis to and from airports multiple times a year, the cumulative volume is significant. More importantly, the taxi-to-public-transport substitution is one of the easiest and most cost-effective interventions in any travel programme.

Source DEFRA 2025. Heathrow Express + Tube CO₂e is illustrative based on UK national rail and London Underground factors. Both taxi and tube include WTT. Costs are approximate indicative ranges.

At programme scale, the impact is measurable. For a mid-size travel programme (15,000 flights per annum), we estimate average annual savings from last-mile optimisation alone of around £145,000 — from switching airport transfers to public transport for the subset of travellers on suitable routes. Emission reductions on those same trips exceed 70% per journey.