  Max-pressure (MP) is a decentralized adaptive traffic signal control approach
that has been shown to maximize throughput for private vehicles. However,
MP-based signal control algorithms do not differentiate the movement of transit
vehicles from private vehicles or between high and single-occupancy private
vehicles. Prioritizing the movement of transit or other high occupancy vehicles
(HOVs) is vital to reduce congestion and improve the reliability and efficiency
of transit operations. This study proposes OCC-MP: a novel MP-based algorithm
that considers both vehicle queues and passenger occupancies in computing the
weights of movements. By weighing movements with higher passenger occupancies
more heavily, transit and other HOVs are implicitly provided with priority,
while accounting for any negative impacts of that priority on single occupancy
vehicles. And, unlike rule-based transit signal priority (TSP) strategies,
OCC-MP more naturally also accommodates conflicting transit routes at a
signalized intersection and facilitates their movement, even in mixed traffic
without dedicated lanes. Simulations on a grid network under varying demands
and transit configurations demonstrate the effectiveness of OCC-MP at providing
TSP while simultaneously reducing the negative impact imparted onto lower
occupancy private vehicles. Furthermore, OCC-MP is shown to have a larger
stable region for demand compared to rule-based TSP strategies integrated into
the MP framework. The performance of OCC-MP is also shown to be robust to
errors in passenger occupancy information from transit vehicles and can be
applied when passenger occupancies of private vehicles are not available.
Finally, OCC-MP can be applied in a partially connected vehicle (CV)
environment when a subset of vehicles is able to provide information to the
signal controller, outperforming baseline methods at low CV penetration rates.
