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National Highways – Dartford Crossing Service


The Dartford Crossing is a major crossing of the River Thames, comprising the Queen Elizabeth II bridge and two tunnels linking up the M25 to the east of London. It’s one of Britain’s most important road crossings, with 50 million chargeable crossings in 2021.

In 2014 the toll booths were removed, with drivers needing to use the Dart Charge payment service before or just after they made a crossing.


The Dart Charge service had been in alpha for almost eight years, having not passed a GDS assessment. In 2021, National Highways awarded contracts for the next generation of the Dart Charge service. The aim was to learn from the live service, apply user-centred design (UCD) principles and address criticisms of the service from users.

The live service generated significant income for the government in its current state; therefore, the challenge was to find ways of improving the user experience working within the established business and policy constraints. The new Dart Charge contract was split into several parts, so Hippo was working with multiple providers and stakeholders, creating challenges around communication and decision-making.


Hippo took a service design-led approach to the work, looking at the whole end-to-end journey to understand the pain points and opportunities across both the digital and non-digital user journeys.

Hippo provided a blended team, working closely with a number of stakeholders in a fully agile way. Over the course of the project, we worked both on the initial payment service and on the user journey for people who hadn’t paid the charge on time.

We took what worked in terms of the existing service but improved the service flow and user experience through constant ideation and iterative improvements.

Our solution addressed the major challenge of how to engage the 5% of users who didn’t pay for their crossings. And our research allowed us to remove the pain points throughout the payment process, making it quicker and easier for people to pay, even if they had accessibility needs.


Hippo’s involvement supported the wider project team to pivot to a more UCD-based approach. We adapted and flexed to the constant changes within the project.

We turned around a large amount of work within very short timescales, where necessary carrying out simultaneous discovery and alpha activity. Although only working on the end-to-end service from October 2021, the alpha assessment was scheduled for mid-January 2022. Hippo’s input allowed the service to finally pass alpha.

Importantly, while carrying out the design work, we also developed excellent working relationships and helped multiple stakeholders to gain a more complete understanding of UCD.


The National Highways Head of Service Assessments said of the Hippo team that

“They were all incredible and worked at the highest standard to get the programme through Alpha. I am truly grateful for all their effort in helping get us over the line”

and, after hearing the service had passed its alpha assessment, thanked Hippo for making it all possible:

“without Hippo, there would be no celebrations”.

The CDDO assessors were also extremely positive about Hippo’s work, saying the team

“had a strong research focus on accessibility and inclusion, including going through alternative recruitment channels to access hard-to-reach participants they have considered the full end-to-end user journey, including the steps before and after the digital service, and this is reflected in their designs”.