We　consider　a　freeway　traffic　network　described　by　the　linearized　Aw-Rascle-Zhang　(ARZ)　model,　which　can　be　monitored　at　the　boundaries　by　a　set　of　sensors.　Inspired　by　the　consensus-based　distributed　filtering　for　the　finite-dimensional　systems,　an　extension　to　the　infinite　dimensional　case　by　using　Lyapunov　techniques　is　studied.　When　consensus　weights　are　known,　we　provide　sufficient　conditions　under　which　the　network　model　is　detectable,　i.e.　for　a　specific　choice　of　consensus　weights　there　exists　a　set　of　filtering　gains　such　that　the　dynamics　of　the　estimation　errors　are　exponentially　stable　for　every　agent.　Some　numerical　studies　provide　a　further　insight　on　the　effects　of　consensus-based　boundary　filtering.