Every car in this series so far has been about a vehicle understanding the world around it on its own — seeing it with cameras, radar and lidar, then deciding what to do about it. V2X (“vehicle-to-everything”) is the other half of the picture: instead of only inferring that the truck three cars ahead just braked hard, the truck could simply tell every car behind it, instantly, over radio, even before their sensors or their drivers notice anything. It sounds like a small difference. In practice it’s the only way to get information that no onboard sensor can ever see — what’s happening around a blind corner, on the other side of a hill, or hidden by the truck in front — and it has already been tested at real scale across Europe.
V2V, V2I, V2N: one umbrella, several conversations
V2X is really a family of links, each with a different partner on the other end. V2V (vehicle-to-vehicle) is car-to-car: a hard-braking event, a hazard light, a sudden loss of traction, broadcast directly to nearby vehicles. V2I (vehicle-to-infrastructure) connects the car to the road itself: a traffic light broadcasting its next phase change so a car can adjust speed instead of guessing, a roadworks sign warning of a lane closure a kilometre before the driver would see the cones, a smart sensor at a blind junction. V2N (vehicle-to-network) is the mobile-network side of the same idea, feeding in traffic, weather and routing information over standard cellular data rather than short-range radio. None of these needs the car to be self-driving to be useful — V2X features are already shipping quietly on ordinary combustion cars as an early-warning layer on top of human driving, well ahead of full autonomy.
The format war nobody outside the industry noticed: DSRC vs C-V2X
For most of the last decade, V2X development has been slowed less by the physics than by a genuine standards fight between two incompatible radio technologies. DSRC/ITS-G5 (Dedicated Short-Range Communications, built on a Wi-Fi-derived standard) was first out of the gate and got the earliest large-scale European pilots. C-V2X (Cellular V2X, built on the mobile-network 4G/5G standard stack) arrived later but had the momentum of the telecom industry and a cleaner upgrade path to 5G behind it. The two are not interoperable at the radio level, so a car built for one cannot talk to roadside infrastructure built for the other — which is precisely the kind of chicken-and-egg problem that has repeatedly stalled wide V2X rollout: nobody wants to install expensive roadside units for a standard that might lose, and nobody wants to fit cars with a radio that has nothing nearby to talk to yet.
The EU actually tested both technologies at scale, years ago
C-MobILE (“Accelerating C-ITS Mobility Innovation and depLoyment in Europe”, 2017-2021, €12.58M, coordinated by IDIADA, Spain) took the DSRC/ITS-G5 side of the story from research pilot to real deployment, elevating existing test sites into working C-ITS services aimed specifically at safety in complex urban areas and for vulnerable road users, with an explicit focus on the interoperability and common approach that a fragmented standard badly needs. On the C-V2X side, 5G-MOBIX (“5G for cooperative & connected automated MOBIlity on X-border corridors”, 2018-2022, €21.41M, coordinated by ERTICO, Belgium) is the largest project of the whole series so far by funding: it ran live cross-border CCAM trials over 5G corridors in multiple EU countries plus China and South Korea, deliberately built to surface exactly the standardisation and spectrum gaps that keep blocking a single European approach. Two sibling projects funded under the same 2018 call ran parallel corridor trials with a narrower focus — 5G-CARMEN (Munich-Bologna corridor, coordinated by Fondazione Bruno Kessler, Italy) and 5GCroCo (France-Germany-Luxembourg corridor, coordinated by CTTC, Spain) — both testing specific latency-critical use cases like tele-operated driving and high-definition mapping updates over the same 5G infrastructure.
Platooning: the use case that proved the communication protocol, even after the business case stalled
The most demanding V2V use case tested at scale in Europe was truck platooning: several trucks driving a fixed short distance apart, electronically linked so they brake and accelerate together like a single very long vehicle, cutting aerodynamic drag and fuel use. ENSEMBLE (“ENabling SafE Multi-Brand pLatooning for Europe”, 2018-2022, €19.78M, coordinated by TNO, Netherlands) drove six differently branded trucks — a first, since platooning had previously only been demonstrated within a single manufacturer’s fleet — in mixed platoons across national borders under real traffic, and worked with regulators to define the road-approval requirements, including V2I communication, that cross-brand platooning would need. The wider commercial rollout of truck platooning has largely stalled since then, for reasons that had little to do with the technology — driver-employment concerns, liability questions, and the difficulty of guaranteeing enough same-route traffic to actually form a platoon on demand. What did survive and get reused is exactly the part relevant to this article: the cross-brand communication protocols, message sets and safety mechanisms ENSEMBLE standardised are the same building blocks now underpinning V2V work well beyond platooning specifically.
The infrastructure side is still an active, funded research line
Unlike some of the more mature topics in this encyclopedia, V2I infrastructure is not a solved problem sitting on a shelf — it’s a live Horizon Europe research line right now. iDriving (“Intelligent & Digital Roadway Infrastructure for Vehicles Integrated with Next-Gen Technologies”, signed 2024, €5.0M, coordinated by the National Centre for Scientific Research “Demokritos”, Greece) is building a prototype specifically for the roads that tend to get forgotten in V2X pilots — secondary rural and urban roads rather than motorway corridors — combining a shared safety-criteria benchmark, common communication solutions across mixed vehicle and infrastructure sensors, and compact, easily deployable sensor packages, precisely because most fatal crashes happen on exactly the kind of road that big-corridor projects like 5G-MOBIX don’t cover.
Why your car probably still can’t talk to the traffic light
Put together, the pattern is consistent: the individual pieces of V2X technology have each been proven, repeatedly, at real scale across Europe. What’s missing is the boring, expensive part — a single agreed radio standard, and enough roadside units and equipped vehicles on the same standard in the same place to make the network effect kick in. Until that critical mass exists locally, a V2X-equipped car is mostly listening to other V2X-equipped cars nearby, which today usually means very few, if any.
Photo: © Car-Shooters