  Airport departure operations constitute an important source of airline delays
and passenger frustration. Excessive surface traffic is the cause of increased
controller and pilot workload; It is also the source of increased emissions; It
worsens traffic safety and often does not yield improved runway throughput.
Acknowledging this fact, this paper explores some of the feedback mechanisms by
which airport traffic can be optimized in real time according to its current
degree of congestion. In particular, it examines the environmnetal benefits
that improved surveillance technologies can bring in the context of gate- or
spot-release aircraft strategies. It is shown that improvements can lead yield
4% to 6% emission reductions for busy airports like New-York La Guardia or
Seattle Tacoma. These benefits come on top of the benefits already obtained by
adopting threshold strategies currently under evaluation.
