Mae rhai risgiau penodol ynghlwm wrth rai rhannau o’r rhwydwaith, fel y twnelau, ac mae angen cynlluniau ymateb brys ar eu cyfer. Mae cynllun digwyddiad mawr wedi’i lunio ar gyfer ardal Twnelau Brynglas sy’n nodi’r camau allweddol a fyddai’n rhan o’r ymateb i unrhyw ddigwyddiad a allai effeithio ar y twnelau ynghyd â swyddogaethau’r ymatebwyr allweddol, gan gynnwys y gwasanaethau brys.
Clearly there are particular risks associated with some parts of the network, such as tunnels, and these require specific response plans.   A major incident plan is in place for the Brynglas Tunnels area, which defines the key actions that would form part of the response to any incident affecting the tunnels and the roles of key responders, including the emergency services.