Security experts say trip poses threats to buildings , bridges , tunnels along route . Comment: Former Secret Service agent says chemical detectors could be installed along route . At inauguration , lone offenders pose greatest risk because of difficulty detecting them .
Security experts say trip poses threats to buildings , bridges , tunnels along route . Environmental groups say terrorists could use chemical plants along route in attack . Former Secret Service agent says chemical detectors could be installed along route . At inauguration , lone offenders pose greatest risk because of difficulty detecting them .