How to compare two technical bids for motorway and major-artery lighting

Overview

Two bids with the same luminaire count and installed power can describe profoundly different installations. On motorways and main extra-urban roads, lighting is concentrated on interchanges, service areas and high-risk sections, where visual continuity is a safety requirement. This methodological comparison by Centro Studi Lumeitalia explains how to read two motorway and major-artery lighting proposals in parallel without stopping at price.

Applicable standards

The regulatory reference for motorway and major-artery lighting is not a single document but a coordinated set of standards covering performance, safety and environmental impact. In design practice the following documents drive the main choices.

• EN 13201-2 — M classes for fast motorised traffic.
• CIE 140 — road lighting calculation methods.
• UNI 11248 — class selection and adaptive downgrading.

Bringing bids onto a common basis

The first step is checking that both proposals assume the same requirements, the same geometry and the same maintenance factor. If one calculates for a new installation and the other at end of life, comparison is impossible until the assumptions are realigned. The same check applies to annual operating hours and the planned dimming profile.

In motorway and major-artery lighting projects, differences frequently arise from a different reading of site conditions: clarifying this point in writing is worth more than any comparison table.

Where the differences hide

• Photometry — File of the proposed luminaire, not an equivalent — Calculation not reproducible
• Maintenance factor — Value and associated cleaning cycle — Below-target performance at end of life
• Control — Protocol, dimming curve, signal-loss behaviour — Declared savings not achieved
• Protection — Coordination and declared withstand — Premature failures outside warranty
• Maintenance — Cycles, access, spares and lead times — Operating cost above budget
• Warranty — Duration, exclusions, validity conditions — Unplanned burden on the client

From price to cost of ownership

A meaningful economic comparison spans the whole operating period: initial investment, annual consumption under the planned dimming conditions, cost of planned maintenance and an estimate of replacements. Energy price and inflation assumptions must be declared: changing them changes the outcome, and undeclared they make the comparison non-reproducible.

The selection criterion must be written before bids are received. Setting parameter weights afterwards is the practice that generates the most disputes in comparative procedures.

Recurring critical points

The difficulties that most often emerge in motorway and major-artery lighting projects are not about product selection, but about defining requirements and verifying results.

• Avoiding abrupt transition zones between lit and unlit sections.
• Keeping maintenance feasible with minimal lane closures.
• Withstanding vibration, de-icing salt and wind loads on high masts.

Design approach

An orderly method drastically reduces variations during works and disputes at commissioning. Three choices make the difference from the earliest stages.

• Transition zones designed with a controlled luminance gradient.
• Luminaires with fast access to the gear tray and replaceable components.
• Remote management for diagnostics and fewer field interventions.

Parameters to verify

• M class — EN 13201-2 — assigned by design speed and complexity
• Surround ratio SR — EN 13201-2 — lighting of the lateral strips
• Maintainability — specification — access without removing the optic
• Mechanical resistance — EN 60598 — vibration and pole loads

Most frequent mistakes

Non-conformities found at commissioning almost always come from three causes: requirements not declared or declared without a reference standard, calculation run on idealised geometry, and an optimistic maintenance factor. All three can be avoided at zero cost during design.

• Same assumptions on requirements, geometry and operating hours
• Maintenance factor aligned across proposals
• Photometric files of the luminaires actually offered
• Maintenance and spare-part items quantified
• Economic assumptions (energy, inflation) declared
• Selection criterion defined before bids are opened

Key takeaways

A motorway and major-artery lighting project holds up over time when requirements are declared, the calculation reproduces real conditions and on-site verification follows an agreed protocol. Component selection matters, but comes later: without measurable requirements even the best product delivers a result that cannot be demonstrated. Centro Studi Lumeitalia makes its technical office available to review requirements and design checks.

Methodological note: This content is written for technical information purposes by Centro Studi Lumeitalia and does not replace the lighting design or a full reading of the standards cited. Applicable performance values are those of the standards in force at design time.

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