## 3 Results
### Emission Rate of CO, HC, NOx, and PM on Diverse Test Mode Characteristics  
Table 4 presents the ER of CO, HC, NOx, and PM obtained during the diverse test mode for each vehicle type. Among the gasoline vehicles, G1 exhibits higher CO ER in the US06 mode compared with other test modes. The US06 mode is a test mode including warm-up (preheating) driving warm-up before test measurement to satisfy the rapid acceleration driving speed, and the analysis was conducted after the vehicle was sufficiently warmed up. During the preheating mode, G1 demonstrated significantly higher emissions than in other test modes. G2, on the other hand, emitted the highest amount of CO in both the NEDC and US06 modes. This result can be attributed to rapid acceleration and deceleration, as well as variations in test mode configurations that may include different starting conditions compared with G1. In the case of LPG vehicles, L2 displays considerable CO ER in the US06 mode. This can be attributed to the increased fuel consumption necessary to overcome the high load demands and achieve the desired driving speeds in the rapid acceleration test mode. Conversely, the reason why L1 has a lower ER than L2 is judged to be influenced by the fuel control technology or aftertreatment device applied to meet the regulation of L1 produced in 2017. Notably, the EURO4 diesel vehicles emit higher levels of all pollutants compared with gasoline and LPG vehicles in the NEDC mode; however, their emission rates remain lower than those of gasoline and LPG vehicles overall. The emission levels of HC in each test mode were analyzed. G1 exhibits the highest HC emissions in the NEDC mode, indicating that a portion of the fuel used during vehicle startup is not fully combusted and subsequently emitted as exhaust gas. This can be attributed to the inclusion of starting conditions in the test mode. Furthermore, the delayed activation of the catalyst due to the gentle driving conditions at the beginning of the NEDC \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Compound** & **Mode** & **G1** & **G2** & **L1** & **L2** & **D6-1** & **D6-2** & **D4-1** & **D4-2** \\ \hline \multirow{4}{*}{CO} & CVS-75 & 634.7 & 204.0 & 101.4 & 500.5 & - & - & - & - \\  & US06 & 2577.0 & 576.0 & 126.0 & 7660.4 & - & - & - & 130.0 \\  & NEDC & 1711.5 & 612.6 & - & - & - & - & 135.0 & 590.0 \\  & WLTC & 1770.5 & 491.7 & - & - & 37.0 & 35.0 & 0.0 & 125.0 \\ \hline \multirow{4}{*}{HC} & CVS-75 & 30.0 & 9.0 & 3.0 & 10.0 & - & - & - & - \\  & US06 & 21.0 & 7.0 & 1.0 & 34.0 & 4.0 & 4.0 & 2.0 & 18.0 \\  & NEDC & 177.0 & 45.0 & - & - & - & - & 17.0 & 78.0 \\  & WLTC & 23.0 & 2.0 & - & - & 8.5 & 12.0 & 4.0 & 21.0 \\ \hline \multirow{4}{*}{NOx} & CVS-75 & 13.0 & 10.0 & 3.0 & 5.0 & - & - & - & - \\  & US06 & 40.0 & 50.0 & 2.0 & 2.0 & 38.0 & 60.0 & 430.0 & 670.0 \\ \cline{1-1}  & NEDC & 40.0 & 10.0 & - & - & - & - & 162.0 & 316.0 \\ \cline{1-1}  & WLTC & 50.0 & 35.0 & - & - & 33.4 & 36.0 & 323.0 & 480.0 \\ \hline \multirow{4}{*}{PM} & CVS-75 & 1.2 & - & - & 0.2 & - & - & - & - \\ \cline{1-1}  & US06 & - & 2.0 & 0.4 & 0.9 & 0.4 & - & 21.4 & 33.0 \\ \cline{1-1}  & NEDC & - & - & - & - & - & - & 18.3 & 29.8 \\ \cline{1-1}  & WLTC & 0.9 & - & - & - & 0.4 & 0.1 & 14.0 & 21.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Emission Rate of CO, HC, NOx, and PM by test mode (mg/km). mode also influenced the HC emissions. Similarly, G2 emits the highest levels of HC in the NEDC mode, with overall lower HC emissions compared with G1 across all test modes. For LPG vehicles, L2 consistently exhibits higher HC emissions than L1 in all test modes. L2 displays significant HC emissions in the US06 mode, which can be attributed to increased fuel consumption and the subsequent emission of unburned HC due to the high load conditions. The EURO6 vehicles are estimated to have high HC emissions before reaching the activation temperature of DOC, a CO and HC abatement device. As a result, the EURO6 vehicles display the highest ER of HC in the WLTC mode.