  Cooperative Adaptive Cruise Control (CACC) systems are considered as key
potential enablers to improve driving safety and traffic efficiency. They allow
for automated vehicle following using wireless communication in addition to
onboard sensors. To achieve string stability in CACC platoons, constant time
headway (CTH) spacing policies have prevailed in research; namely, vehicle
interspacing grows with the speed. While constant distance headway (CDH)
spacing policies provide superior potential to increase traffic capacity than
CTH, a major drawback is a smaller safety margin at high velocities and string
stability cannot be achieved using a one-vehicle look-ahead communication. The
hypothesis of this work is to apply CDH only in few driving situations, when
traffic throughput is of highest importance and safety requirements can be met
due to comparably low velocities. As the most relevant situations where CDH
could be applied, we identify starting platoons at signalized intersections. In
this paper, we illustrate this idea. Specifically, we compare CTH with CDH
regarding its potential to increase the capacity of traffic lights. Starting
with the elementary situation of single traffic lights we expand our scope to
whole traffic networks including several thousand vehicles in simulation. Using
real world data to calibrate and validate vehicle dynamics simulation and
traffic simulation, the study discusses the most relevant working parameters of
CDH, CTH, and the traffic system in which both are applied.
