## 2 Materials and Methods
### Laboratory Setting
We focused mainly on the values measured in the B50L photometric test point, as this is the geometric point that corresponds to the oncoming driver's eyes; therefore, it is used to assess the amount of glare. Figure 2: Two-lane night-time traffic simulation laboratory. (**a**) Driver’s viewpoint of the laboratory—the left “opposing lane” with a carousel simulating an oncoming vehicle, and the right “driver’s lane” with the driver’s light sources and target eye charts placed at a distance; (**b**) driver’s placement in the laboratory. For the actual experiment, the black curtain completely covered the white wall. The light samples used in the experiment were thus as follows:  
* series reflector containing regular H7 bulb (CCT of 3200 K);
* series LED projector module (\"white\" LED, CCT of 5700 K);
* \"yellow\" adjusted LED projector module--module containing a PCB with the most yellowish LED color bin and the lens defocused to create the most blurred cut-off line possible while maintaining the headlamp legality as much as possible (CCT of 4700 K);
* \"blue\" adjusted LED projector module--module containing a PCB with the most bluish LED color bin and the lens focused to create the sharpest cut-off line possible while maintaining the headlamp legality as much as possible (CCT of 6200 K). For the oncoming vehicle, all the samples were used as sources of glare (in a random order for each participant). For the driver's own headlights \"illuminating the road ahead\", only the series LED projector module and the H7 bulb reflector were used, in order to minimize the number of possible combinations with the oncoming vehicle's headlamps. Tables 2 and 3 show the photometric values and gradients for the left and right light samples, respectively. It needs to be stressed that the halogen bulb reflectors were measured directly as whole headlamps including the covering glass, whereas the LED modules were measured in special holders without the covering glass. This was due to the fact that they were built via a prototyping process and repeated mounting and dismantling of the whole headlamp would steadily damage the plastic parts of the headlamp. However, it can be approximated that the real values (that would be found in measurements with the covering glass) are around 10% lower than those measured. Further, all of the LED modules were measured on the same level of driving current, as only two electronic control units (ECUs) were used to simplify the experimental procedure (i.e., the same for all three modules). This caused a different luminous intensity achieved in the B50L glare point of each module. Namely, the left yellowish LED module achieved higher values for the B50L photometric point than are imposed by the homologation requirements. Nevertheless, the value is still in the CoP (Conformity of Production) limit and, moreover, the real value is lower due to the Fresnel reflections on the covering glass. Therefore, the B50L photometric value would still be legal. The HV point value of this module would not be legal; however, in the experiment, the HV point is far from the observer's eyes and probably does not influence the results. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Photometry Test Point** & **Homologation Value** & **CoP Value** \\ \hline HV & max. 625 cd & max. 880 cd \\ BR & max. 1750 cd & max. 2100 cd \\ B50L 1 & max. 350 cd & max. 520 cd \\
50L & max. 18,480 cd & max. 15,840 cd \\ \hline
75R & min. 10,100 cd & min. 8080 cd \\ \hline \hline \end{tabular}  
* Oncoming driver glare point. These photometric values are derived with the use of the standard V(\(\lambda\)) curve.  
\end{table} 
Table 1: Homologation and Conformity of Production (CoP) photometry requirements in candelas for several photometry test points.