Will the façade dazzle tram drivers on George Street?

570 George Street, Sydney. A solar reflectivity and glare assessment of the western façade facing the light rail corridor, following the Hassall (1991) method.

≤13% external visible reflectivity across all façade materials,
below the TfNSW 15% maximum

Ladybug model of the Sydney CBD block with the western façade of 570 George Street coloured by annual direct sun hours, red to dark red — Annual direct sun hours on the western façade (Ladybug)

Building type: Commercial building, CBD
Location: 570 George St, Sydney NSW
Receptor: Light rail drivers, 1.8 m eye height
Method: Hassall (1991), City of Sydney glare guidance
Criteria: Lv ≤ 500 cd/m², TI ≤ 15%, reflectivity ≤ 15%
Tools: Ladybug, Honeybee, Radiance / evalglare

Overview

Light rail runs along George Street directly beside the building’s western façade. Sunlight reflected from glazing or metal cladding can reach a driver’s eye and reduce their ability to see the track and signals. This study tested the proposed façade against the Sydney glare criteria from two driver positions.

The challenge

Sydney receives high annual solar exposure, and the SRC-TMYx data for Observatory Hill shows direct radiation arriving mostly from the north-west and west in the afternoon. That is when the western façade is most likely to reflect sun into the corridor, so the assessment focused on clear-sky afternoon conditions at the solstice and equinoxes.

Where the sun hits the façade

The upper and westernmost zones receive the most sun. These are the surfaces tested as potential glare sources in the driver views.

Sun-path dome over the city block with reflected sun rays traced from the façade toward the street — Critical sun positions and reflected rays toward the corridor

Honeybee radiation map of the block with the western façade coloured orange and yellow — Annual incident solar radiation on the façade (Honeybee)

Façade materials

External visible reflectivity from manufacturer data, checked against the Transport for NSW limit. Where product data was missing, conservative values based on AS/NZS 1580.602.2 were used.

Ground-floor shopfront glazingClear laminated

10%

Upper-floor vision glazingClear / low-E IGU

12%

Vertical fins and mullionsDark anodised aluminium

10%

Spandrel and cladding panelsMedium-dark anodised aluminium

13%

External signageMatt aluminium, vinyl graphics

<15%

0%TfNSW limit 15%20%

All five material groups comply. Signage is limited to the building’s existing dark bronze anodised finish or matt materials, with no illuminated, mirrored or high-gloss elements.

Glare at the driver’s eye

Threshold increment (TI) is calculated with the Hassall / CIE relationship TI = 65 × L_v / L_ad^0.8, from the veiling luminance (L_v) and adaptation luminance (L_ad) at each driver position.

False-colour fisheye luminance map from the northbound driver position

View 1, northbound driver

Afternoon, 2–3 pm, clear sky

Veiling luminance: 906 cd/m² limit 500
Adaptation luminance: 13,855 cd/m²
Threshold increment: 28.6% limit 15%

Above both limits. Flagged for further review and mitigation at this approach.

False-colour fisheye luminance map from the southbound driver position

View 2, southbound driver

Afternoon, 2–4 pm, clear sky

Veiling luminance: 226.45 cd/m² limit 500
Adaptation luminance: 13,857.5 cd/m²
Threshold increment: 7.2% limit 15%

Within both limits.

Conclusion

Every façade material visible from the light rail corridor sits below the TfNSW 15% reflectivity limit, and the southbound driver view meets both glare criteria. The northbound view exceeds the veiling luminance and threshold increment limits in the early afternoon, so that approach is the one to address, through façade detailing or further analysis, before the design is finalised.

The study shows why glare is worth testing from the driver’s actual position: a compliant material schedule alone does not guarantee a compliant view.

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