Adaptive Limited Look-ahead Optimization of Network Signals – Decentralized
(ALLONS-D)
Porche (33) proposed a decentralized adaptive traffic signal control method called
ALLONS-D in his dissertation. ALLONS-D is based on a depth-first branch and bound
algorithm and uses a decision tree to help find the best control sequence (33). The
decision tree used in ALLONS-D is similar to the one used in DYPIC as shown in
Figure 7, in which each node represents a decision point and has a cost value associated
with it while each arc is a control action. Figure 7 only shows the decision tree for an
isolated intersection with two-phase control. For intersections with four or more phases,
the size of the decision tree will make exhaustive search methods infeasible for real time
applications. To improve searching efficiency, ALLONS-D uses the branch and bound
algorithm and a special technique called “Serve the Largest Cost” (STLC) to find the
best control sequence. The entire optimization process of ALLONS-D can be divided
into two parts: 1) initial decision path (sequence) building, and 2) backtracking and
exploration.