This paper considers the data delivery delay problem in wireless sensor networks. The delivery delay is a significant measure when the data freshness is the first concern of users. The goal of this paper is to route delay-sensitive data to mobile nodes (M nodes) within an allowed latency. The data collection system is composed of a set of M nodes amounted on buses, a set of sensor nodes to detect the interested phenomenon and a set of special nodes deployed at bus stops to assist data routing. An optimization-based approach called improved-unusual message delivery path construction (I-UMDPC) is proposed. Considering the actual features of bus operation, two aspects of uncertainties are accounted in our approach: 1) the bus arrival time and 2) the stop duration. Extensive simulations as well as practical experiments on our testbed demonstrate that I-UMDPC is able to route delay-sensitive data reliably and efficiently and performs better than existing work.