I started by trying to understand what the core problems were for both the business and the end-users. This included mapping out the current user journeys using simple stories to help highlight the pain points. I also spent some time mapping out basic journeys for each mode of transport I could think of to find patterns to create a simple, consistent flow for a multi-modal solution that would require minimal tuition to use.
Once a suitable flow was agreed upon, I worked with the client and development team to prioritise features based on effort and value. I was then able to start fleshing out some ideas on the visuals, seeking feedback from developers regularly to avoid technical constraints.