Zombie Cars do mean the death of the Car – Autonomous Vehicles will worsen Congestion

A remarkably evidence free and ill informed  article in the Telegraph from Madeline Grant

The death of the car has been greatly exaggerated – yet ministers still want to bury it

We’ve bet the farm on a future without cars, when in fact there will be more than ever

I explained in an earlier article why electric vehicle will still cause a major environmental problem.

The key problem with self driving cars is them getting from customer A to customer B – the so called Zombie Car problem.

Paul Priestman

you’re just going to get traffic jams full of autonomous vehicles with nobody in them as they go to pick up other people,” he said. “It’s going to exacerbate the situation rather than improve it.”

Which is why the Paris Deputy Mayor wants to ban them.

Currently you have cars driving 5% of the time and parking 95% of the time – a wastful use of land in central areas.  Imagine of they were driving 95% of the time and parking 5% of the time.  Hence the Zombie Car Problem.

But this issue isnt a simple one.  In the future cars will be of two types.  People in their own self driving cars and people sharing self driving cars.  The trend has been very much to the latter however it is still likely that the former will be predominant.

Individual self driving cars drive far more cautiously than humans and leave greater space between vehicles.  For this reason at first self driving cars will increase congestion according to DOT research here in the UK.


The Department for Transport predicted a “decline in network performance” once one in four cars become driverless.

However, should driverless vehicles make up between 50% and 75% of cars, DfT researchers say they will reduce congestion.

The DfT said early models of the vehicles acted more cautiously and the result could be a “potential decrease in effective capacity” on motorways and A roads.

But as more people adopted the technology and it became common place on the country’s road network, the study found that congestion could be cut by 40%.

The reason being that if a self driving car detects it is behind another self driving car it can drive in a troupe with minimum space between vehicles, more predictable breaking can also reduce phantom traffic jams caused by poor breaking propagating in waves. .   However self driving vehicles can add to vehicle driven miles where there is no guaranteed parking space at the end of a trip when the self driving car can drive further out to find one and further in going to pick up the driver.  Likely to be a common occurrence in cities with on street parking.  Owners could also send their zombie cars on errands like picking up shopping, delivering parcels, dropping off dry cleaning or picking up children from school. They also of course could use them after drinking when they wouldn’t otherwise drive.

So the issue is whether the positive congestion effect of individual self driving vehicles will be cancelled out by the negative effect of shared self driving vehicles.  The issue is even more complicated as ride hailing services may displace taxis and one thing is for sure taxis have an enormous amount of ‘dead heading’ that is driving around looking for customers.

Research by Schaller consulting in New York found:

1. Passenger trips increased by 15 percent from 2013 to

2. Vehicle miles increased by 36 percent, reflecting trip
growth, a trend toward longer trips and lower
utilization rate.

3. Traffic speeds declined 15 percent overall, and by 18
percent during the day.

4. The number of taxi/TNC vehicles in the CBD increased
by 59 percent from 2013 to 2017.

5. Taxi and TNC vehicle hours spent transporting
passengers increased by 48 percent from 2013 to 2017

6. Unoccupied taxi/TNC vehicle hours grew by 81
percent from 2013 to 2017.

To what extent will autonomous vehicles increase ride hailing?

John Zimmer, CEO of ride hailing service Lyft predicts that in 5 years’ autonomous ride hailing will be ubiquitous in cities “and by 2025, owning a car will go the way of the DVD.”

One report suggests that by 2030 95% of US miles will be via shared vehicles

Its a linear programming problem – if autonomous vehicle use does rise above 50% then the gains to congestion will be obliterated if shared use rises above a 4:5 ratio according to the research.

Even if there were gains to congestion again experience and theory suggests that as consumers seek to minimise their misaligned cost of travel and housing costs they will drive further on less congested roads to access cheaper housing, or switch from transit, leading to the reappearance of congestion.  Exactly the scenario created by the first introduction of cars leading to sprawl and the distopian nightmare of car dependent megacities.   We are already seeing declines in Metro ridership in major cities such as New York and London with a danger of a death spiral of worsening services and fer ridership.

Transport planning needs to adapt to encourage trips from autonomous vehicles that don’t increase congestion, such as outside peak hours and to transit hubs, from those that do.  We can use a combination of pricing charges and incentives and ‘ridership as a service’ apps – linking transit and ride hailing in a single seamless service.  We can for example, charge more highly for single occupancy and empty occupancy vehicles and ensure they arnt exempt from congestion charging (as should neither be taxis).  We can restrict free surface level parking and encourage shared charged multiple level parking where autonomous vehicles can park between trips rather than deadheading.

There is some irony that the libertarian wet dream of individualized transport depends on being enslaved to robot cars and requires ubiquitous behavior changing taxes to make work in the first instance.