Filtered Values vs Relevant Benchmark Data - FILTER based on a SELECTEDVALUE?

Are the 2 data sets joined?

Do you have the road type benchmarks at road type level?

If  not maybe you can create a dax table at road type level. Then join the road to this new table using the roadtype.

You can use something like this to add a dax table. Goto Modelling and click table.

RoadTypeSummary = 
ADDCOLUMNS(
    SUMMARIZE(
        'RoadBenchmarks'
		,RoadBenchmarks[RoadType]
	)
	,"DataX",CALCULATE(COUNTROWS(DataX))	
	,"DataY",CALCULATE(SUM(RoadBenchmarks[DataY]))
	,"SDDataY",CALCULATE(STDEV.P(RoadBenchmarks[DataY]))
	)

You can then join to your road table.

It should filter with the road.

You can write dax from this on the road table or bring in the benchmark data to the road table using the RELATED function.

This makes it easy to write expressions that compare the current and benchmark values.

Also if you don't need it you can hide the summary table to keep the model a bit simpler.