Lighting

Allow for a battery life of at least 1.5 times the expected duration of the ride to ensure a safety margin. Most USB lights offer 2 to 10 hours of battery life depending on the mode used: maximum power mode consumes 3 to 5 times more power than the energy-saving flashing mode. For a 3-hour ride in winter, a light with 5 to 6 hours’ battery life in normal mode is sufficient. For longer rides (night-time cycle races, night-time rides), opt for a model with a removable external battery or carry a spare USB battery. Modern lights have a charge indicator: make sure to check this before every ride.

A lumen measures the total luminous flux emitted by the light source, whilst a lux measures the illuminance received on a surface at a given distance. A 500-lumen light with a narrow beam concentrates all its light onto a small area and produces a high lux level at close range. The same light with a wide beam illuminates a larger area but with fewer lux per m². In practice, lumens are the most commonly displayed figure. For a cyclist, what matters is the effective range and beam width: a well-designed 300-lumen wide-beam light provides better illumination in real-world conditions than a 500-lumen narrow-beam light with poor diffusion.

For any cyclist riding more than twice a week, the USB-rechargeable option is significantly more economical and practical. A set of AA batteries lasts 3 to 6 hours depending on the brightness setting, amounting to €5 to €15 per month for a daily commuter. A rechargeable light charges in 1 to 3 hours via USB (computer, charger, power bank) and costs a fraction of a penny per charge. Almost all high-quality lights sold today are USB-C or micro-USB rechargeable. Batteries remain useful for emergency lighting (lightweight, always ready), for cycling trips far from power sockets, or for occasional cyclists.

Yes, daytime running lights (DRL) in flashing mode significantly improve visibility to motorists. Road studies show that cyclists equipped with a flashing daytime light are spotted 2 to 3 times earlier by vehicle drivers. Most modern lights have a DRL or Blast mode (150 to 300 lumens in rapid flashing) specifically designed for daytime use. Battery life in DRL mode is often 10 to 15 hours, making it suitable for long rides. For the front light, a daytime flashing mode is particularly useful in low-contrast conditions (overcast skies, tunnels, mist).

For cycle touring and intensive commuting, the hub dynamo is the most reliable long-term solution. It is powered by the rotation of the wheel, provides constant lighting without ever running out of battery, and can power a USB charger to recharge other devices. However, the installation cost (€150 to €300 including hub and lights) is high, and it is permanently fitted to the bike. For commuting 3 to 4 times a week over short distances, a USB-rechargeable light of 600+ lumens is more than sufficient. A dynamo is justified when consistent lighting is critical: multi-day trips, commuting in all weathers, long winters.

A rear light with a laser projection on the ground or 270° wide visibility is the current gold standard for road safety. Lights such as the Lezyne Laser Drive project two red laser lines onto the road surface on either side of the bike, visually marking the safety zone for approaching motorists. COB (Chip-On-Board) LED lights emit a wider beam than standard LEDs, visible at 270°. For road use, a rear light with 50 to 100 lumens in flashing mode is visible from 1 to 2 km away. Mounting the light as high as possible (on the seat post rather than the lower seat stays) optimises visibility for motorists, whose view is often obstructed by the bonnet.

The flashing mode is more visible from a distance, whilst the steady mode is more effective for seeing the road. At the rear, the flashing mode is unanimously recommended: it attracts more attention from motorists and consumes 3 to 5 times less energy. At the front, a steady light allows you to see the road, but an additional flashing light or DRL makes the cyclist more visible to oncoming vehicles. A pure flashing light at the front is not recommended at night as it does not allow you to see obstacles. The ideal combination: a powerful steady front light (300+ lumens) + a red flashing rear light.

Manufacturers offer specific adapters for oval or flat aero handlebars; check the diameter. Aero handlebars have an oval or D-shaped cross-section that does not fit standard round clamps (31.8 mm). Brands such as Garmin, Lezyne and Bontrager offer adapter kits with silicone straps or magnetic bases compatible with flat surfaces. Check compatibility before purchasing: some lights come with two clamps (round handlebar + aero handlebar), whilst others require an adapter sold separately. Mounting systems with universal rubber straps (Knog, BBB) fit almost all handlebar profiles.

The French Highway Code requires a white or yellow front light and a red rear light, which are mandatory from dusk onwards and in poor visibility. The front light must be visible from 150 metres away, and the rear light from 150 metres as well. Reflectors (white at the front, red at the rear, and orange on the pedals and spokes) are also mandatory. Failure to comply with these requirements is punishable by a first-class fine (€11). However, cycling in flashing mode only (without a steady mode) is not explicitly prohibited, but the use of steady mode is recommended to comply with the spirit of the regulations.