Smart City Light — what municipalities should clarify before their first tender

Multifunctional poles and sensors turn street lighting into data infrastructure. What Swiss municipalities should look at: data protection under cantonal law, open interfaces, demand-based lighting and life-cycle costs.

Today a street luminaire is often more than a light source. It carries sensors or radio nodes and is controlled from central software. That changes the questions a municipality should answer before going to tender: what data is generated, who may use it, and will the installation remain expandable over its entire service life?

Data protection: cantonal law applies

For municipalities, the primary reference is their canton’s data protection act. The revised Federal Act on Data Protection (FADP), in force since 1 September 2023, governs data processing by private persons and federal bodies. The EU’s GDPR is not the starting point for a Swiss municipality.

The principles are nonetheless similar everywhere and can be read from the FADP: process data only proportionately and for a recognisable purpose, destroy or anonymise it once it is no longer needed, and build data protection in from the planning stage. Anyone who systematically monitors extensive public areas must carry out a data protection impact assessment beforehand under the FADP.

In practice, this means first checking whether a purpose can be achieved without personal data. A sensor that merely counts vehicles or pedestrians and does not make anyone identifiable is not covered by data protection law. Cameras, by contrast, require a formal decision under cantonal rules that states who monitors where and when, and how long recordings are kept. Involving the cantonal data protection office early avoids changes later.

Open interfaces instead of vendor lock-in

Luminaire, sensor module and control software rarely come from the same supplier and have different life cycles. To make sure they work together and can be replaced individually, open standards belong in the tender:

• Zhaga Book 18 with D4i: the standardised connection between outdoor luminaire and sensor or communication module, both mechanical and electrical. D4i extends DALI-2 with luminaire, energy and diagnostic data. Parts are interchangeable when both luminaire and module carry the Zhaga-D4i mark.
• ANSI C136.41: the receptacle for plug-in control modules with five or seven contacts, dimming via 0–10 V or DALI.
• TALQ: an open interface between central management software and field devices. The specification is freely available and is meant to prevent a city from remaining tied to one manufacturer for every extension.

Only as bright as necessary

Sensors are above all a tool for demand-based lighting. The recommendations of the Federal Office for the Environment (FOEN) on avoiding light emissions (2021) rest on the precautionary principle of the Environmental Protection Act: light only as brightly as necessary, control according to demand, and reduce or switch off at times. As an example, the FOEN describes luminaires dimmed to an orientation level that rise to the standard level together with their neighbours when movement is detected.

The lighting requirements still apply. On traffic routes SN EN 13201 governs, supplemented in Switzerland by the SLG 202 guideline of the Swiss Lighting Society. A dimming strategy is therefore part of the lighting design, not merely a setting in the software.

Tender by function and life cycle

Municipalities procure under cantonal law based on the Intercantonal Agreement on Public Procurement (IVöB 2019), where the canton has joined it. It allows services to be described by function and performance, requires international standards where possible and permits brand names only with the addition “or equivalent”. Besides price, life-cycle costs, sustainability and functionality are expressly provided for as award criteria.

With connected lighting this pays off in particular: evaluating energy consumption, maintenance and the later replacement of individual modules over the service life compares offers more realistically than the purchase price alone.

Support for municipalities

The Smart City Switzerland programme of EnergieSchweiz supports cities and municipalities free of charge with information, networking, tools and project funding. SANTEC engineers and supplies luminaires and multifunctional poles that work with dynamic lighting controls such as esave, and is glad to clarify interfaces and lighting design ahead of a tender.