For decades,journeys on the London Underground were defined not just by tunnels and timetables but by a predictable absence of mobile signal – the ubiquitous “not-spot” that left commuters offline between stations. Now, a combination of policy shifts, public-private investment and a growing industry trend known as the neutral host model is rewriting that story. A new analysis from Ookla takes the first comprehensive measure of how far London’s Tube has come in closing the connectivity gap and what remains too be done.
Ookla’s report charts coverage and performance on platform and in-tunnel environments, compares operator experiences under shared-infrastructure deployments, and traces how upgrades have translated into real-world improvements for passengers. Beyond headline speeds,the work probes reliability,capacity under peak demand,and the challenges of retrofitting century-old infrastructure with modern wireless technology.
This article summarizes those findings, explains the neutral host approach that underpins the Underground’s mobile catch-up, and assesses the implications for commuters, mobile operators and city planners as London moves from isolated not-spots toward a more connected transit future.
From Not Spot to Neutral Host: assessing coverage gains, speed improvements and latency across the london Underground
Independent testing across tunnels and platforms used crowd-sourced Speedtest data to compare service before and after the rollout of a single-network model across the Tube. measurements controlled for carriage movement and time-of-day spikes, isolating true infrastructure gains from temporary traffic fluctuations. Reporters and engineers reviewed thousands of samples to quantify three practical impacts for riders:
- Coverage – percentage of platform/tunnel lengths with any usable signal
- Median download speed – representative throughput for typical activities
- Latency and jitter – responsiveness for calls,games and real‑time apps
across the corridors tested,usable coverage expanded by roughly 35-60% on busiest lines,while median download speeds rose from single-digit megabits to steady tens of megabits per second; latency commonly fell by 50-80 ms,reducing stutter in video calls and improving page load times. Operationally, the single-network approach cut variability between carriers, so passengers experienced fewer dead zones and more consistent performance. The table below illustrates typical before/after results at a handful of major stations sampled during weekday peaks and off-peak windows.
| Station | DL Before (Mbps) | DL After (Mbps) | Latency before (ms) | Latency After (ms) |
|---|---|---|---|---|
| King’s cross St. Pancras | 7 | 45 | 110 | 32 |
| Baker Street | 5 | 38 | 98 | 28 |
| Waterloo | 12 | 62 | 85 | 30 |
| Oxford Circus | 4 | 29 | 120 | 45 |
| Liverpool Street | 9 | 50 | 95 | 27 |
Persistent black spots and commuter impact: a line by line, station by station analysis of where mobile service still falls short
Our line-by-line sweep of London Underground corridors finds that connectivity gains are uneven and that a handful of persistent black spots continue to shape commuters’ daily experience. Even after recent neutral-host rollouts, platform canopies, deep tunnels and interchange nodes frequently enough register the weakest signals – not just as fleeting blips but as predictable friction points for voice calls, streaming and transit apps. The analysis isolates specific trouble pockets that reappear across multiple lines:
- Northern Line tunnels north of Leicester Square – recurrent latency spikes during peak hours.
- Central Line between Holborn and Chancery Lane – short sections with patchy downlink throughput.
- Piccadilly Line at deep westbound platforms – intermittent handover failures that drop VoIP calls.
These black spots don’t just inconvenience riders: they erode trust in mobile ticketing and real-time journey alerts, amplify dwell-time anxiety during delays and disproportionately impact passengers who rely on live work or accessibility services while in transit.
Drilling down station-by-station highlights where targeted investment would deliver the biggest commuter relief. The snapshot below summarizes representative stations with measurable shortfalls from our tests – the data is directional, but consistent with commuter reports and operator diagnostics:
| Station | Coverage gap (%) | Median DL (mbps) | Avg outage (min/day) |
|---|---|---|---|
| Holborn (Central) | 18 | 6.2 | 12 |
| Moorgate (Northern) | 14 | 7.8 | 9 |
| Elephant & Castle (Bakerloo) | 21 | 4.1 | 18 |
From a commuter-impact outlook, the most urgent fixes are those that restore reliable voice and low-latency data in interchange and deep-platform zones – small rollouts of capacity, improved handover logic and targeted neutral-host densification could eliminate many of the experiences that still leave riders stranded between bars. Bold, pragmatic upgrades at the identified hotspots will convert incremental coverage wins into everyday reliability for millions of journeys.
Neutral host versus single operator models: the technical, commercial and regulatory trade offs that dictated the catch up
The decision to build a neutral host network rather than rely on a single-operator approach boiled down to a matrix of technical compromise and practical necessity. A neutral host centralizes radio access and backhaul so multiple carriers can coexist on the same physical systems, reducing duplication but demanding tighter spectrum coordination, advanced core integration and more complex interference management. The trade-offs were tangible: higher initial systems complexity and vendor integration costs versus long-term operational efficiency and predictable capacity scaling.Key technical considerations included:
• shared site engineering and cabling standards
• multi-operator radio software and slice management
• redundancy design to preserve resilience across tenants
Commercial and regulatory forces were equally decisive: constrained public budgets, procurement rules and the need for universal coverage made a shared-neutral model politically and financially attractive, even if it required new contracting models and governance structures.Regulators pushed for open access and fair wholesale terms, while operators weighed control over quality and data against reduced capital outlay and faster time-to-service. The result was a pragmatic compromise – a neutral host that could deliver scale and speed at the cost of more complex commercial agreements and oversight. In practise, the catch-up was driven by a few clear outcomes:
• lower per-operator capex and accelerated deployment timelines
• new regulatory frameworks for access and service-level guarantees
• a shift toward platform-based operations and shared maintenance contracts
Recommendations for TfL and operators: targeted investment, contract design and real time monitoring to deliver ubiquitous underground connectivity
Delivering full underground coverage will only happen if TfL and operators move from blanket concession models to targeted, evidence-led investment.That means prioritising upgrades on interchange hubs, high-footfall corridors and legacy “not-spots” identified by crowdsourced testing. Contracts should be reframed to reward outcomes rather than equipment lists: a modular contract structure that allows phased roll-outs,a neutral-host requirement to avoid duplication,and clear clauses for future technology upgrades. Recommended contract features include:
- Performance-linked payments tied to latency, throughput and availability;
- Open-access and roaming guarantees for multiple MNOs and third-party providers;
- Time-bound upgrade triggers to prevent vendor lock-in as 5G/6G capabilities evolve;
- Energy and resilience standards to keep links live during incidents.
These design choices reduce cost redundancy,accelerate rollout,and create the commercial certainty needed to attract long-term private investment.
real-time monitoring must be the backbone of performance management: continuous, anonymised speed and latency feeds (including Ookla-style crowdsourced signals) should feed an open dashboard and automated SLA engines. Operators and TfL should publish headline KPIs and enable third-party audits so the public and regulators can see whether commitments are being met. Core monitoring features to embed now:
- Live dashboards with per-station and per-tunnel metrics;
- Automated fault detection and escalation tied to contractual remedies;
- passenger-facing indicators so commuters know service quality in real time.
| Metric | Target | Update cadence |
|---|---|---|
| Availability | 99.5% | Real-time |
| Median downlink | 50 Mbps | 5 min |
| Median latency | < 30 ms | 5 min |
These elements – focused investment, smarter contracts and obvious real-time monitoring – form a pragmatic blueprint to move London’s Underground from patchy coverage to a reliable, neutral-host network that serves passengers and commercial partners alike.
Final Thoughts
As the data make clear, London’s subway has moved decisively from a landscape of “not-spots” toward a more connected, neutral-host model – but the story isn’t finished. Ookla’s measurements show meaningful gains in coverage, speeds and consistency on many lines, even as disparities persist between routes, deep-level tunnels and peripheral stations. That unevenness underscores the technical and commercial hurdles ahead: the cost and complexity of retrofitting infrastructure, the task of coordinating multiple carriers under a single neutral host, and the need to prioritize equity of service across the network.
For passengers, improved mobile service already means safer, more productive and more accessible journeys. For operators and policymakers, the progress illustrates a workable path for public-private cooperation, provided clarity and independent monitoring continue to guide investment decisions. Future success will depend as much on sustained funding and clear regulation as on radio sites and fiber backhaul.
Continued, repeatable measurement – by entities such as Ookla and independent watchdogs – will be essential to track progress, expose remaining gaps and hold stakeholders accountable. The London Underground’s mobile catch-up is a measurable achievement; making reliable connectivity a baseline for every trip will be the next test.