Security forces say trip creates threats to buildings , bridges , tunnels along route . Environmental groups say terrorists could use chemical weapons along route in attack . And there are non-traditional vulnerabilities : scores of bridges and tunnels that could be sabotaged . 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 forces say trip creates threats to buildings , bridges , tunnels along route . Environmental groups say terrorists could use chemical weapons 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 .