The spectral optimization of phosphor-coated white LED (pc-WLED) with green and orange phosphors excited by blue chip for road lighting was investigated based on the mesopic limited luminous efficacy (LLE) and IES (the Illuminating Engineering Society of North America) color fidelity index (R). The average LLE of four road lighting standards of the USA and the UK decreases as R increases, but the optimal scotopic/photopic ratio increases slightly with R increases for a given correlated color temperature (CCT). The average LLE could reach the highest of 339  lm/W for R=70, 326  lm/W for R=80, and 309  lm/W for R=90 at CCT=5000  K. Six real pc-WLEDs with different R at CCT≈5000  K and with R≈70 at different CCT were demonstrated. Compared with current pc-WLEDs with yttrium aluminum garnet doped with Ce (YAG:Ce) phosphors, the average LLE of six demonstrated pc-WLEDs will be over 5.0% and above. So, it is suggested that the road lighting should choose pc-WLEDs with high efficiency green phosphors (520-530 nm) instead of YAG:Ce phosphors.

Congestion road condition is an important factor that must be considered in urban traffic path planning, while most path planning algorithms only consider the distance factor, which is not suitable for the current complex urban traffic congestion road condition. In order to solve the above problems, this paper proposes a dynamic path planning method based on improved ant colony algorithm in congested traffic. The method quantifies the main attributes of urban road length, number of lanes, incoming and outgoing traffic flow, and introduces the road factor used for replacing the distance parameters of particle swarm optimization and ant colony algorithm. In the method, the particle swarm algorithm can effectively optimize the parameters of the ant colony algorithm, and significantly improve the efficiency of ant colony algorithm, such that it is more applicable for dynamic path planning application to greatly reduce the congestion rate of path planning. In addition, this paper selects some intersections in the Beijing area to carry out the dynamic path planning experiment based on the improved ant colony algorithm under congested road conditions. The experimental results show that, compared with the ant colony algorithm based on distance parameter, the proposed dynamic path planning method can effectively reduce the average congestion rate ranging from 9.73% to 13.63%.

The photometric model for the mesopic luminous efficacy (LE) of hybrid white LEDs, including the radiant efficiency of both blue and red LEDs as well as the overall quantum efficiency of the phosphor layer or the quantum dot (QD) film, was developed. The optimal spectral parameters of integrated with quantum dots (QD-WLED), phosphor-converted white LED (pc-WLED) with red LEDs instead of red phosphor (pc/R WLED) for both color fidelity index (R) and color rendering index (R) above 70, 80, and 90 at correlated color temperatures of 2700-6500 K were obtained by maximizing the average LE of four road lighting standards. By comparing among pc-WLED, QD-WLED, and pc/R WLED, it was suggested that the pc/R WLEDs make strong candidates for mesopic road lighting. The requirements of the overall efficiency of QD film were presented if the QD-WLEDs were competitive to the pc-WLEDs. Finally, the three real pc/R WLEDs with both R and R about 80 at CCTs of 2982 K, 4560 K, and 5683 K were demonstrated.