Responsible lighting

All bat species occurring in Finland are protected under the Nature Conservation Act and are listed in Annex IV of the EU Habitats Directive; therefore, their living conditions must not be degraded.

In valuable bat areas and along bat commuting routes, unnecessary lighting should be avoided during bats’ active season from early May to the end of September. Bats become active at sunset and move mainly during twilight and darkness.

Of the bat species most commonly observed in Tampere, the Northern bat is relatively tolerant to lighting, whereas Myotis species are more sensitive. For these species, a lit path or bridge may act as a barrier to movement. Daubenton’s bats forage over water surfaces, making it particularly important to prevent light spill onto water bodies.

The use of warm light colours, precise light distribution, and correct dimensioning are essential. Luminaire-level control systems enable seasonal switching off and dimming recommended for bat habitats.

Other species groups sensitive to artificial light include birds, insects, and fish. Among birds, nocturnal species such as owls are particularly sensitive to lighting, but artificial light also affects other species by disrupting migration, increasing collision risks, and advancing breeding cycles.

Insects are attracted especially to ultraviolet, blue, and green wavelengths; therefore, cool light tones should be avoided. When insects are drawn into areas of artificial light, they are exposed to predation and their natural feeding and mating behaviour is disturbed. Nocturnal pollinators in particular suffer from light pollution, and plant pollination success may be reduced in illuminated areas.

Fish and amphibians may also be attracted to artificial light, increasing their exposure to predators. Artificial light has not been shown to affect flying squirrels or otters.

In general, moderate use of artificial light is always beneficial for nature. 

Areas sensitive to artificial light are locations where there is a need to reduce the negative impacts of lighting on fauna. These areas can often remain unlit without compromising safety or functionality.

Unlit areas should form coherent entities, allowing users to bypass them by choosing an alternative illuminated main route. The illuminated route must not cause obtrusive light to spread into areas intended to remain dark.

Areas intended to remain dark include:

• nature conservation areas
• sites included in nature conservation programmes
• core natural areas identified in the master plan
• valuable bat habitats

In Tampere, over 40 areas are protected under the Nature Conservation Act. Near the city centre, examples include Pyynikki and Viikinsaari.

Areas with restricted lighting use include:

• currently illuminated areas with identified natural values
• other extensive green areas that are currently unlit
• the central park network defined in the master plan
• significant watercourses and their buffer zones

Obtrusive light refers to light that extends beyond the intended illuminated area. It causes irritation, discomfort, impairs the visibility of essential information, and creates environmental disturbance. Undesirable effects of outdoor lighting include sky glow, glare, and uncontrolled light spill.

The most effective opportunities to limit obtrusive light occur during the design phase. When planning public outdoor lighting in Tampere, luminaires must be selected, positioned, and aimed so that lighting technical requirements are met while minimizing overdimensioning and light spill (e.g., towards building windows or the sky).

Key sources of obtrusive light include:

• light directed horizontally or above the horizontal plane,
• indirect upward-reflected light from illuminated surfaces.

Modern LED luminaires provide high luminous efficacy, well-designed optics, and excellent control capabilities. When correctly designed and aimed, LED lighting produces significantly less obtrusive light. In Tampere, all new lighting installations are equipped with control systems enabling dimming, significantly reducing obtrusive light levels during nighttime low-traffic hours.

In demanding locations—particularly near areas sensitive to artificial light—the client requires obtrusive light assessments supported by lighting calculations. Compliance with obtrusive light requirements must be demonstrated through lighting calculations.

Night-time lighting requirements apply between 23:00 and 05:00, taking dimming levels into account. Limit values for E‑area classifications are presented in Table 14.

In addition, designers are required to assess both discomfort glare and disabling glare using:

• G-values (upward light and disabling glare),
• D-values (discomfort glare). 

The following ecological lighting measures may be selected for each project in cooperation with the client (see map appendices 7 and 8 for area-specific guidance):

Lighting design measures:

• Light output and optics are precisely dimensioned; light does not spread unnecessarily into the surroundings.
• When possible, one lower lighting class than recommended is used.
• Correlated colour temperature is 3000 K; the only exception is sports fields, where 4000 K may be used. In justified cases, even warmer light (2700 K) may be used, particularly in waterfront areas.
• Upward light ratio (ULR) is minimized and verified through lighting calculations consistent with the area’s E-class.
• Disabling glare (G4–G6) and discomfort glare (D4–D6) are verified through lighting calculations.
• Lighting installations are measured post-installation using illuminance and/or luminance meters, visually assessed, and reported to the client.
• Luminaire-level control readiness is ensured to allow future adjustments.
• Lighting is dimmed at night according to the City of Tampere’s dimming tables.
• In bat habitats, it must be ensured that treetops are not illuminated.
• Natural shorelines should remain unlit.
• Under-bridge lighting is not permitted in areas with known bat commuting routes.

Lighting control measures in sensitive areas:

• In bat habitats, lighting is dimmed to 20% between 21:00 and 07:00 from early May to the end of October.
• Night-time switch-off is applied during the active bat season from early May to the end of September between 23:00 and 05:00.
• Sports and park fields and outdoor exercise routes are switched off between 22:00/23:00 and 06:00.
• Lighting is switched off for the summer period (June–July)

In addition, projects should prioritize environmentally friendly and durable products (luminaires, poles, foundations, etc.).

On routes intended to remain dark, visibility may be improved by using light-coloured gravel and white edge posts. Posts or structures may also be painted with photoluminescent paint, which emits light for 6–10 hours in darkness.