RUNNING ON EMPTY: What will autonomous vehicles do when empty and why they should NEVER be allowed to rank
- Perry Richardson
- May 7
- 3 min read
The biggest unanswered question around autonomous vehicles (AV) in London is not actually whether the technology works. It is what happens when those vehicles are not carrying passengers.
If large fleets of AVs or robotaxis are eventually licensed in London and across the UK, operators will need somewhere for them to wait between jobs, recharge, clean, undergo inspections and reposition for demand. Unlike a human minicab or taxi driver, an empty AV has no reason to stop working. The commercial model pushes it to keep moving or stay strategically placed near busy areas.
That creates a potential congestion risk. Empty “dead running” already contributes significantly to traffic from private hire vehicles. An autonomous fleet could increase that if vehicles continuously circulate while waiting for the next booking rather than paying for parking space.
London is especially vulnerable because road space is already constrained. There is very little spare kerbside capacity in central areas. Boroughs are actively removing parking bays to widen pavements, install cycle lanes and create loading space. Even today, conventional PHV drivers struggle to find legal areas to just stop for a short break. Hundreds or thousands of autonomous vehicles would intensify that pressure unless tightly regulated.
Charging infrastructure is another problem. AV fleets will almost certainly be electric because the economics only really work with EV running costs. But rapid charging space in London is already contested. Fleet operators would likely require dedicated depots outside central London where vehicles could queue, recharge and undergo maintenance. That means AVs may spend considerable time travelling empty between operating zones and charging hubs.
Outside London, the issue changes slightly but does not disappear. Many UK cities have more available land for depots and off-street waiting areas, but they often have weaker public transport networks and more car dependency. That increases the risk that autonomous services add total vehicle mileage rather than replace private car ownership. Rural operations would be even harder because low demand means more empty repositioning miles between fares.
This is where taxi ranks become politically and legally contentious.
Under long-established UK taxi law, taxi ranks exist for licensed hackney carriages that are legally entitled to ply for hire. In London, black cabs can accept immediate street hails and work from designated ranks. Private hire vehicles cannot. They must be pre-booked through a licensed operator.
That distinction matters because ranks are not parking spaces. They are part of the legal framework governing immediate hire availability. A vehicle sitting on a rank signals to the public that it is available for instant hire without prior booking.
If autonomous vehicles operating under a PHV-style or app-booking model were allowed onto taxi ranks or create something similar, the entire regulatory separation starts collapsing. A passenger seeing an empty AV waiting on a ‘rank’ would reasonably assume it is available immediately. Even if the booking technically happens through an app seconds before entry, regulators would face accusations that the operator is effectively plying for hire by another route and physically displaying the vehicles availability.
There is also the issue of accountability and compliance. Taxi ranks are governed by detailed local rules covering vehicle licensing, driver conduct, accessibility obligations and enforcement. Human taxi drivers can be inspected, directed by marshals, moved on by police or spoken to by compliance officers. A driverless vehicle complicates all of that. Who becomes responsible if the vehicle blocks a rank, causes obstruction or waits illegally?
London taxi ranks were also designed around a regulated public transport function. Black cabs provide wheelchair-accessible transport, assistance for vulnerable passengers, and legally enforceable obligations around carriage refusal. TfL has indicated that current autonomous systems do not yet meet London taxi or private hire licensing standards for passenger carriage.
If AV operators gain access to taxi ranks without meeting full hackney carriage obligations, they effectively receive the commercial benefits of taxi infrastructure without accepting the regulatory burdens taxi drivers carry. That would be viewed by many in the trade as simply unacceptable.
The likely long-term outcome is that autonomous services, if approved, will need their own operating framework. That may include dedicated pickup zones, geofenced waiting areas, remote depots and strict limits on zero-occupancy circulation. Otherwise cities risk fleets of empty vehicles continuously roaming dense areas searching for the next fare while competing for already scarce road space.
