Segment extraction in QGIS for roadkill sampling

I need to conduct a survey along a road network to sample roadkill occurrences. I want to sample 5% of the total road network extent for feasibility reasons. I divided the road network by road type (primary, secondary, tertiary and neighborhood) and road number. Each type is a proxy of traffic flow and represent a different percentage of the total road network. I would like to extract segments of a fixed length at random along each road type. Is there any way to select random segments along a single line vector ?

I tried the basic methods of random extract within subsets but it only extracts features, and I'm struggling to put equidistant points along the lines. I thought by doing so I could then select a random set of segments delimited by said points.