--- title: "What is grey fleet? The hidden fleet most employers forget they run · Kerbway" description: "Grey fleet is staff driving their own cars on work business, and it is probably your biggest, oldest and least-managed fleet. Here is what it costs, who carries the risk, and how to reduce it." url: https://www.kerbway.com/news/what-is-grey-fleet/ --- Blog # What is grey fleet? The hidden fleet most employers forget they run Grey fleet is staff driving their own cars on work business, and it is probably your biggest, oldest and least-managed fleet. Here is what it costs, who carries the risk, and how to reduce it. ![](https://www.kerbway.com/static/rachel-percival.g5_qwvNx_Z1agK0J.webp) Rachel Percival CCOO & Co-founder [Rachel Percival on LinkedIn](https://www.linkedin.com/in/rachel-percival-4b81745/) [Rachel Percival on Email](mailto:rachel@kerbway.com) ![A man walks in a city parking lot filled with various cars, offering a busy urban scene.](https://www.kerbway.com/static/cover.CVhC2Ns-_PGMv2.webp) Ask a fleet manager how many vehicles they run and they will count the vans, the pool cars and the leases. The biggest fleet in most organisations never makes that list, because the organisation doesn’t own a single vehicle in it. ## What is grey fleet? **Grey fleet** is any privately owned vehicle used for business journeys, typically an employee’s own car, driven on work trips and claimed back at a pence-per-mile rate. Commuting doesn’t count; the site visit, the cross-town meeting and the community appointment do. It is called _grey_ because it sits in a grey area: the organisation pays for the mileage and carries legal responsibility for the journey, but the vehicle itself is invisible: nobody procured it, nobody maintains it, and in many organisations nobody has checked it is roadworthy or insured for business use. ## How big is the UK’s grey fleet? Bigger than almost anyone assumes. The last major national study, _Getting to Grips with Grey Fleet_, produced by the Energy Saving Trust for the BVRLA, put it at around **14 million cars, roughly 40% of all vehicles on UK roads**, covering some **12 billion business miles a year** and costing employers about **£5.5 billion annually** in mileage claims and car allowances.¹ The public sector alone accounted for around **1.5 billion grey-fleet miles and £786 million a year**, driven largely by NHS, local-authority and civil service staff.¹ In NHS primary care the fleet is almost entirely grey fleet, covering an estimated **155 million miles every year**.² ## What does grey fleet actually cost? More than the mileage claim suggests and, as of this year, noticeably more than it used to. From April 2026 HMRC’s approved mileage rate rose from 45p to **55p per mile** for the first 10,000 miles, the first increase since 2011.³ Every grey-fleet mile now costs a fifth more overnight, before you add: - **Admin:** collecting, checking and processing per-mile claims across hundreds of drivers. - **Compliance overhead:** licence, insurance and MOT checks done properly (see below), or risk carried silently if they aren’t. - **No asset in return:** unlike a pool vehicle, the spend buys no capacity. It is pure per-mile cost, and it rises with every journey. Meanwhile, most organisations that _do_ own pool cars leave them idle for the vast majority of the week, paying twice: once for the parked asset, once for the grey-fleet mile that replaced it. ## Who is responsible when staff drive their own cars for work? The employer. Under the Health and Safety at Work Act 1974, the [duty of care for work-related driving](https://www.kerbway.com/news/duty-of-care-staff-own-cars/) applies **exactly the same** whether the vehicle is company-owned, leased, hired or the employee’s own car.⁴ In practice that means being able to evidence that every grey-fleet driver holds a valid licence, that the vehicle is taxed, MOT’d and roadworthy, and that the driver’s insurance covers **business use** (ordinary social-domestic-and-commuting cover does not). Research suggests only around one in three organisations run these checks regularly.⁴ If a grey-fleet driver has a serious incident on a work journey and the paperwork isn’t there, it is the employer answering the questions. ## Why does grey fleet matter for net zero? Because grey-fleet cars are old. The average grey-fleet vehicle is **8.2 years old**, against roughly 18 months for a typical company car: older, more polluting and less safe than almost any alternative.¹ Nationally the grey fleet was estimated to emit **3.6 million tonnes of CO2 a year**, plus around 8,000 tonnes of NOx, about twice the emissions of London’s entire bus fleet.¹ That is why grey-fleet reduction is now written into public-sector policy: every NHS trust and integrated care board must have a sustainable-travel strategy in its Green Plan by the end of 2026, and council fleet-decarbonisation strategies routinely name the grey-fleet-to-shared-EV-pool shift explicitly.² ## How do you reduce grey fleet? The playbook is well established: 1. **Measure it.** Baseline your grey-fleet miles, cost and CO2\. Most organisations have never totalled it. 2. **Remove the journeys you can.** Online meetings, better scheduling, public transport and active travel for the trips that suit them. 3. **Shift the rest onto vehicles you control.** A shared pool of vehicles you own or lease, booked and unlocked self-service so it is easier than taking your own car, turns an unmanaged per-mile cost into a measured, compliant, decarbonisable fleet. Step three is where most schemes fail: if booking a pool car means a key cabinet, a sign-out sheet and a walk to reception, staff will keep driving their own. Making the pool fleet the path of least resistance is exactly what Kerbway does for [councils](https://www.kerbway.com/solutions/local-authorities/), [NHS trusts](https://www.kerbway.com/solutions/nhs/) and [businesses](https://www.kerbway.com/solutions/smes/): keyless access, in-app booking, automatic driver checks and the utilisation and CO2 reporting to evidence the reduction. > Grey fleet is the only fleet that gets bigger the less you manage it. The moment you measure it, the case for sharing the vehicles you already run makes itself. > > Rachel Percival, Kerbway Want the numbers for your own organisation? Our [Grey-Fleet Cost & Carbon Calculator](https://www.kerbway.com/resources/grey-fleet-cost-carbon-calculator/) puts a cost and a CO2 figure on your grey-fleet miles and models what a shared pool of the vehicles you already run would save. Notes // Citations // Disclosures 1. Energy Saving Trust for the BVRLA, _Getting to Grips with Grey Fleet_: fleet size, mileage, cost, vehicle-age and emissions estimates. 2. NHS England, _Net Zero Travel and Transport Strategy_: primary-care grey-fleet mileage and the 2026 Green Plan sustainable-travel requirement. 3. HMRC Approved Mileage Allowance Payments, 2026/27 tax year: 55p per mile for the first 10,000 business miles (25p thereafter), effective 6 April 2026. 4. HSE guidance on driving for work and RoSPA, _Driving for Work: Own Vehicles_: employer duty of care for grey-fleet journeys; TTC Group research on the proportion of employers running regular document checks. ## More news - Blog ## [Who holds the duty of care when staff drive their own cars?](https://www.kerbway.com/news/duty-of-care-staff-own-cars/) A staff car on a work trip counts as a place of work. What councils and NHS trusts must check, who holds the duty, and where a pool car helps. Marc Roberts 13 November 2026 - Press Release ## [Kerbway launches with £500,000 to bring fleet sharing to UK organisations](https://www.kerbway.com/news/kerbway-launches-shared-pool-fleet-service/) New B2B mobility company targets NHS trusts, local authorities and property developers, with five founding pilot opportunities available. Kerbway 4 November 2026 - Blog ## [Keyless access: why the phone is the new car key](https://www.kerbway.com/news/keyless-access-phone-as-car-key/) Keyless access puts the pool car key on a phone. How it ends key cupboard delays, helps protect pool car tax status, and what to ask before you switch. Marc Roberts 19 October 2026 ## See Kerbway on your own fleet Book a demo and we will show you how keyless access, booking and reporting work on your pool vehicles, owned or leased. [Book a demo](https://www.kerbway.com/contact/)