A light-reflecting article having an average total reflectivity of at least about 93%, e.g., at least about 95%, for light in a 400 to 700 nanometer wavelength range comprises a thermoplastic or thermoset polymer matrix, such as an acrylonitrile-butadiene-styrene-based matrix, in which is dispersed reflective filler particles such as rutile titania and a flame-retardant material. The flame-retardant material may contain a particulate metal oxide synergist, e.g., antimony trioxide or antimony pentoxide, and a quencher such as a brominated organic compound, e.g., bis(tribromophenoxy)ethane. The polymer matrix and filler may be selected so that their respective refractive indices and the size range of the filler particles satisfies a mathematical relationship having as a function thereof the mean freespace (vacuum) wavelength of the light range being reflected. The article may comprise a light-reflecting enclosure (14) of an illumination source (10), the enclosure (14) having at least one linear aperture (16) formed therein and enclosing a linear light source (12).