UCL report on Gig economy drivers and riders at heightened risk of traffic collisions
The emerging issues for management of occupational road risk in a changing economy: A survey of gig economy drivers, riders and their managers
UCL research primarily based on qualitative information (interviews and online surveys) rather than quantitative historical data. 
Conducted by University College London's Centre for Transport Studies this report includes evidence that those working in the "Gig Economy" (people who are self-employed and choose the hours they work rather than work set contracted hours) increasingly use powered two-wheelers (PTWs), such as mopeds or e-bikes. There is an increasing demand for couriers and delivery drivers to use PTWs especially in cities, where their size allows them to navigate congested streets efficiently compared to vans and heavy goods vehicles. The UCL research also highlights growing risks such as little or no road safety worthiness checks or training, driver distraction, and driver fatigue.