Thanks Bruce and Jayanta for the reply. But, it does not appear to want to work using any value for the search radius. I'm only able to get the spatial join to run is with no value in the search radius.
May have to open a support ticket.
Snippet of the code used
outPoints = "PointsAlongRoutes"
joinFeats = "MergedRoutes"
outJoinFeat = "PointsJoinedToRoutes3"
joinOp = "JOIN_ONE_TO_ONE"
joinType = "KEEP_ALL"
fieldMapping = ""
matchOption = "INTERSECT"
searchRadius = "10 Feet"
distanceField = ""
arcpy.SpatialJoin_analysis(outPoints, joinFeats, outJoinFeat, joinOp, joinType, fieldMapping, matchOption, searchRadius, distanceField)