Roads Without Signals: What the Twin City Promises and What It Does Not

What would happen if we removed the traffic light, not because it failed, but because vehicles had learned to negotiate among themselves? In March 2016 a research team including researchers from the Massachusetts Institute of Technology published a study in PLOS ONE saying that a junction based on time "slots" could double throughput and cut delays. The idea is attractive, but let us read what the study actually said.

How Does a Signal-Free Junction Work?

Instead of waiting for a green light designed for the worst case, each vehicle reserves a time "slot" for crossing through a link to a system that coordinates vehicles arriving from every direction. A "digital twin" can support this: a virtual copy of the system, fed by real-world sensors, on which one can try things before applying them.

The researchers concluded that this approach "could double" capacity and reduce delay. But the result is a mathematical analysis of a crossing of two roads, assuming random vehicle arrivals and set safety distances, and no experiment on real junctions has confirmed it. It is harder to generalise where connected vehicles mix with human-driven ones and pedestrians.

Where Has the Experiment Reached in Our Country?

In October 2025 a robotaxi service was launched in Riyadh through a partnership between WeRide and Uber, on a route between Roshn Front and Princess Noura University, with a permit from the Transport General Authority and a safety driver on board in the first phase, to move later to driverless operation. This is a controlled trial, not a city without signals, and between the two lies a distance that regulation and testing must cover before the technology does.

Zero Crashes: What Does the Figure Really Say?

Self-driving is often justified by the figure "94% of crashes are caused by human error". Its source is a 2015 report by the US road-safety agency, which assigned a driver-related "critical reason" in roughly 94% of about 2.19 million estimated crashes. But the report itself cautions that this label is not intended to identify the cause of a crash or to assign blame to the driver. The figure is a premise, not an argument; the safety of self-driving vehicles should be judged by independent test records. For more on this figure and on the safety of self-driving vehicles, see the article "The Self-Driving Car: What It Promises and What It Does Not Guarantee".

And if the algorithm decides in place of the human, who bears the consequence when it errs: the manufacturer, the operator or the regulator? In most legal systems this is an open question, and it deserves an answer before wide deployment.

Congestion May Return by Another Door

A 2011 study by Duranton and Turner on American cities found that vehicle-kilometres travelled on intercity highways rise in proportion to the lanes added. From this comes our inference, not the study's finding: smoother flow may attract extra trips and bring the congestion back. It is therefore wise to look at the reasons for trips themselves, such as where people live, work and obtain services, and at public transport alternatives, rather than at speeding up movement alone.

Governance Before the Sensor

A digital twin of a city means dense movement data. Collecting it can be a tool of convenience, or it can become surveillance unless bound by minimal collection, anonymisation and a limited retention period; for the wider frameworks of privacy protection see "Privacy in the AI Era". Wisdom suggests starting with defined corridors and open standards among manufacturers, then measuring the effect before expanding.

Success here is measured by what truly benefits people: shorter journeys, fewer crashes and privacy preserved. It is a success we ask God to make possible.