In this paper, the IES file was measured by applying a secondary optical lens to a 21 W LED engine, and the lighting calculation software RELUX was used to perform simulations with the data file of this measurement. For two-lane (two way) concrete paved roads, six LED engine are applied to each streetlight and simulation results show that Uo (uniformity) 0.56, UI (longitudinal uniformity) 0.86 and TI (threshold iIncrement) 9% which satisfies the required standards. RELUX was also used to LED streetlights by designing them in three dimensions, that is ±25% of the arm length of 2.8 m standardized by the road lighting standards of the Korea Expressway Corporation. Comparative analysis was carried out on adjustments were made in increments of 0.1 m that Uo, UI, and TI values in the range of arm lengths from 2.1 m∼3.5 m. For the arm length range of 2.1 m∼2.4 m, Uo was high, whereas UI was low. Therefore, we present the optimal light distribution values designed for an arm length of 2.5 m.

Road lighting has emerged in importance as an essential system to secure safety and visibility for drivers and pedestrians. According to the Road Lighting Standards (KS A 3701), the luminance uniformity (U0) should be 0.4, the luminance uniformity for lanes (UI) should be 0.5, and a threshold increment (TI) of 10% should be satisfied. In this study, we conducted simulations using the Relux program in which the secondary optical lens was applied to a 21 W engine. Ten LED engines were installed on a two-way four-lane road, and the simulation result satisfied the requirements with U0 0.47, UI 0.63 and TI 8%. The U0, UI, and TI were compared with the angle of the LED streetlight varied in the range of 9° ~ 15° with 0.5° intervals. The range was selected as ± 25% of the standard inclination angle of 12° according to the Road Lighting Standard. The U0 was high and the UI and TI were low when the tilting angle was in the range of 9.5° ~ 10.5°. Consequently, an optimum-design of lighting distribution was obtained for the concrete two-way four-lane road when the inclination angle was 9°.