<Map 
  background-color="#808080"
  srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">

    <Style name="My Style" comp-op="src-over">
        <Rule>
            <LineSymbolizer stroke-width="30" stroke="rgba(255,255,255,1)" stroke-linecap="round" stroke-linejoin="round" comp-op="dst-over" />
        </Rule>
    </Style>

    <Layer name="layer" srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">
        <StyleName>My Style</StyleName>
        <Datasource>
            <Parameter name="type">csv</Parameter>
            <Parameter name="file">../data/crossing-lines.csv</Parameter>
        </Datasource>
    </Layer>

</Map>