# Radial and Oblique Impact Testing of Alpine Helnets onto Snow Surfaces
## 3 Results  
Snow sample collection and testing were completed over two non-consecutive days. The first collection was made at 09:00 in the morning when the ambient temperature was 2 \({}^{\circ}\)C. The second collection was made at 09:00 in the morning when the ambient temperature was 6 \({}^{\circ}\)C, and the third collection was made later that same day at 12:00 noon when the ambient temperature was 12 \({}^{\circ}\)C.  
A total of 15 vertical drop tests were conducted with up to two repeats per condition (Table 1). For the snow samples collected in the morning that was not placed in the freezer, all tests resulted in similar mean peak linear headform accelerations, ranging from 77 to 82 \(g\), regardless of headform condition. Mean peak linear headform acceleration was significantly (\(p=0.005\)) lower for snow samples collected at noon compared to snow samples collected in the morning (Table 2). For tests of the large-size helmet, the frozen snow sample resulted in a higher mean peak linear headform acceleration when compared to the non-frozen snow sample, but the result was non-significant (\(p=0.120\)).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{\begin{tabular}{c} **Snow** \\ **Sample** \\ **Collection** \\ \end{tabular} }} & \multirow{2}{*}{\begin{tabular}{c} **Ambient** \\ **Temperature** \\ **[\({}^{\circ}\)C]** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Freezer Time** \\ **[Hours]** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Headform** \\ **Condition** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **\(N\)** \\ **Condition** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Peak Linear** \\ **Headform** \\ **Acceleration [g]** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} \\ **(\(N\)** \\ **Acceleration [g]** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} \\  
For the snow samples collected at noon, large amounts of snow were displaced during a test; therefore, only one test was performed per sample resulting in a total of three tests. The first drop test from 1.5 m, which corresponds to an impact speed of 5.4 m/s, displaced a large amount of snow from a sample collected in the morning and impacted the base of the sample box. Therefore, this test was excluded, and no further tests were performed from the 1.5 m drop height.  
A total of six oblique impact tests were conducted, with one repeat per condition (Figure 4). The mean horizontal sled velocity, as measured by the light gate, was 6.0 m/s (SD: 0.1 m/s). The recreational alpine sports helmet with no RDS had the highest mean peak angular headform acceleration of 7291 rad/s\({}^{2}\). The recreational alpine sports helmet with RDS had the lowest mean peak angular headform acceleration (4056 rad/s\({}^{2}\)), which was significantly (\(p\) = 0.002) lower than the value for the helmet with no RDS. The ski racing helmet had a mean peak angular headform acceleration of 4884 rad/s\({}^{2}\), which was significantly (\(p\) = 0.006) lower than the recreational alpine sports helmet with no RDS.