Weihua Gu

The Hong Kong Polytechnic University | PolyU · Department of Electrical Engineering

Surrogate‐based traffic signal optimization (TSO) is a computationally efficient alternative to simulation‐based TSO. By replacing the simulation‐based objective function, a surrogate model can quickly identify solutions by searching for extreme points on its response surface. As a popular surrogate model, the ensemble of multiple diverse deep lear...

When making route decisions, travelers may engage in a certain degree of reasoning about what the others will do in the upcoming day, rendering yesterday's shortest routes less attractive. This phenomenon was manifested in a recent virtual experiment that mimicked travelers' repeated daily trip-making process. Unfortunately, prevailing day-to-day t...

Autonomous trucks offer a promising avenue for enhancing the efficiency and reducing the environmental impact of road freight transportation. This paper examines a transitional phase towards a fully unmanned truck fleet, focusing on a platooning approach with a lead driver. We develop a novel optimization model for autonomous truck platooning that...

The technology-enabled ride-pooling (RP) is designed as an on-demand feeder service to connect remote areas to transit terminals (or activity centers). We propose the so-called "hold-dispatch" operation strategy, which imposes a target number of shared rides (termed the ride-pooling size) for each vehicle to enhance RP's transportation efficiency....

As electric buses become increasingly popular, it is imperative to optimize the schedules of electric buses with explicit consideration of their charging requirements. Unfortunately, existing studies failed to properly model the impacts of essential operating factors, including the time‐of‐use (TOU) electricity price, partial charging, and limited...

Long bus queues at busy stops plague bus systems in many cities. Since berths are laid-out in tandem, buses' overtaking maneuvers are often prohibited or restricted, which can significantly reduce a bus stop's discharge capacity. When overtaking is allowed, aggressive drivers may perform disruptive oblique insertion maneuvers that would undermine s...

The critical bottleneck affecting a terminal’s oil throughput capacity is shifting from the limited number of berths to the channel connecting the berths to the anchorage area. This is especially true for the terminals with a one-way channel where large oil tankers can navigate through the channel only at high tides. Buffers can be installed at tho...

An autonomous vessel train features several autonomous vessels sailing together, piloted by a conventional, manned leader vessel. It is a promising transitional solution at the present technological level before full autonomy is realized. We develop mixed-integer programming models for jointly optimizing the autonomous vessel assignment to vessel t...

As an eco-friendly transportation option, bike-sharing systems have become increasingly popular because of their low costs and contributions to reducing traffic congestion and emissions generated by vehicles. Due to the availability of bikes and the geographically varied bike flows, shared-bike operators have to reposition bikes throughout the day...

Waterborne transport is known to have low environmental impacts compared to other modes. This paper investigates the optimal container subsidies for shippers to promote intermodal shipping involving waterways in a regional transportation network. We consider a linear subsidy scheme consisting of a fixed-rate component and a variable component propo...

The prevalence of shared bikes in many cities is a double-edged sword to the local mass transit services. Some transit patrons may switch to cycling, causing declines in the transit ridership. Others may benefit from using bikes instead of walking to access transit. The complicated interactions between the two modes entail the necessity of designin...

Transit vehicles operating under skip-stop service visit only a subset of the stops residing along a corridor. It is a strategy commonly used to increase vehicle speeds and reduce patron travel times. The present paper develops a continuous approximation model to optimally design a select form of skip-stop service, termed AB-type service. The model...

Signal priority and exclusive bus lanes are common measures used to promote bus travel at signalized intersections. However, these bus priority measures create significant damage to the car traffic especially at intersections with heavy bus and car traffic. For this reason, bus priority is not welcome at busy intersections. We examine a novel inter...

An efficient two-stage heuristic approach is developed for solving the fleet management problem under time-varying demand. Stage 1 of the approach optimizes the vehicles’ utilization schedule. Continuous-time approximation is employed to yield a set of near-optimality conditions that can greatly reduce the solution space of this stage. Stage 2 then...

Transit vehicles operating under skip-stop service visit only a subset of the stops residing along a corridor. It is a strategy commonly used to increase vehicle speeds and reduce patron travel times. The present paper develops a continuous approximation model to optimally design a select form of skip-stop service, termed AB-type service. The model...

We develop detailed simulation models for examining how various seaside infrastructure improvement measures of a marine crude oil terminal can increase its maximum oil throughput, reduce tanker delays, and minimize the total system cost over a certain planning horizon. The models account for special navigation constraints for oil tankers, realistic...

Lanes used by taxis and other shared-ride vehicles at airports and rail terminals are often congested. The present paper examines congestion-mitigating strategies for a special type of lane inside of which taxis are prohibited from overtaking each other while dropping-off patrons. Taxis must therefore often wait in first-in-first-out (FIFO) queues...

Transit systems are designed in which access and egress can occur via a shared-bike service. Patrons may walk to shared-bike docking stations nearest their origins, and then cycle to their nearest transit stations where they deposit the bikes. The travel pattern is reversed when patrons cycle from their final transit stations on to their destinatio...

A novel Bayesian approach is proposed for estimating the maximum queue lengths of vehicles at signalized intersections using high-frequency trajectory data of probe vehicles. The queue length estimates are obtained from a distribution estimated over several neighboring cycles via a maximum a posteriori method. An expectation maximum algorithm is pr...

We examine special lanes used by taxis and other shared-ride services to drop-off patrons at airport and rail terminals. Vehicles are prohibited from overtaking each other within the lane. They must therefore wait in a first-in-first-out queue during busy periods. Patrons are often discharged from vehicles only upon reaching a desired drop-off area...

We develop analytical approximations for the bus-carrying capacities at near- and far-side stops with one or multiple curbside berths where buses operate in a dedicated bus lane. The approximations are derived using time-space diagrams of bus trajectories and probabilistic methods. They correctly account for the effects of key operating factors tha...

This study develops a Bayesian spatial generalized ordered logit model with conditional autoregressive priors to examine severity of freeway crashes. Our model can simultaneously account for the ordered nature in discrete crash severity levels and the spatial correlation among adjacent crashes without fixing the thresholds between crash severity le...

The urban transit system in a real city usually has two major components: a sparse express (e.g. rail) network and a dense local (e.g. bus) network. The two networks intersect and interweave with each other throughout the city to furnish various route options for serving transit patrons with distinct ODs. The optimal design problem of this bimodal...

It is widely observed in urban areas that major transit corridors often consist of multiple transit systems (e.g., regular street bus, bus rapid transit (BRT), and rail transit) partly or mostly overlapping along the corridor, on which local and express services are simultaneously provided to all transit patrons. Traditional transit corridor design...

We formulate a general bottom-up model for the joint optimization of maintenance, rehabilitation, and reconstruction (MR&R) schedules for a system of heterogeneous pavement segments under budget constraints. The objective is to minimize the total costs incurred to both the highway users and the pavement management agency. We propose a Lagrange mult...

Transit systems in which buses or trains always visit each and every stop along corridors are compared against those that feature two alternative vehicle-dispatching schemes. The alternatives entail so-called skip-stop and express/local services. Continuous models found in the literature are expanded so that the alternatives could be compared under...

Spatiotemporal analyses of freeway sites in Part I have shown that special-lane access points are prone to become bottlenecks. These can degrade traffic flows, sometimes in all lanes. Part II explores select impacts of re-designing the means of entering and exiting a special lane, and of altering the policy governing its use. Parametric tests were...

Most special-use freeway lanes in the US, whether reserved for carpools, toll-paying commuters or both, are physically separated from the adjacent regular-use lanes by some form of barrier. Vehicle movements in and out of a special lane of this type are permitted only at select access points along the route. The barrier at each select point might o...

Various obstructions exist that can impede maximum vehicle flow through signalised intersections. Examples include buses or freight vehicles dwelling at loading areas near the intersection, stalled vehicles, pre-signals that temporarily block car traffic to provide bus priority, on-street parking manoeuvres and permanent road fixtures. If the effec...

Feng, X.; Wang, M.; Li, Y.; Gu, W., and Zhang, Y., 2015. Optimal throughput of crude oil terminals with options for infrastructure improvements. Crude oil is a major commodity transported through ports. Determining the optimal throughput level of crude oil terminals is crucial for efficient utilization of coastal resources and sustainable developme...

Models are formulated to predict the added vehicle and person delays that can occur when a bus stop is located a short distance upstream or downstream of a signalized intersection. Included in the set of models are those that predict the expected delays that cars collectively incur when a bus blocks one of multiple lanes while loading and unloading...

We consider curbside bus stops of the kind that serve multiple bus routes and that are isolated from the effects of traffic signals and other stops. A Markov chain embedded in the bus queueing process is used to develop steady-state queueing models of this stop type, as illustrated by two special cases. The models estimate the maximum number of bus...

Upon having loaded and unloaded their passengers, buses are often free to exit a multiberth bus stop without delay. A bus need not wait to perform this exit maneuver, even if it requires circumventing one or more other buses that are still dwelling in the stop’s downstream berths. Yet, many jurisdictions impose restrictions on bus entry maneuvers i...

Bus stops are often placed short distances upstream of signalized intersections. Buses that dwell at one of these so-called near-side stops can impede queued cars upstream from discharging through the intersection during green times. Residual car queues can form at the intersection as a result. The smaller the distance between a stop and its inters...

Widening a highway toll plaza, border crossing or other checkpoint by adding travel lanes and vehicle-processing stations in parallel fashion can be expensive, and sometimes even infeasible. Rather than expanding laterally, checkpoint capacities can be increased by branching or staggering the vehicle-processing stations, or by placing them in tande...

The maximal rates that buses can discharge from bus stops are examined. Models were developed to estimate these capacities for curbside stops that are isolated from the effects of traffic signals. The models account for key features of the stops, including their target service levels assigned to them by a transit agency. Among other things, the mod...

Large amounts of documents are exchanged during the construction phase of projects, which covers the important management information. To utilize the exchanged documents to support decision-making of the management staffs, the requirement analysis was carried out based on the interviews to the practitioners. A decision support system called Explyze...

The National Stadium will be the main stadium of the Olympic Games of Beijing 2008. The general contractor of this project, Beijing Urban Construction Group Co., Ltd. has adopted EPIMS as the information management system for the multi-party stakeholders in this project, and Tsinghua University is supposed to make some improvement on the system to...

Chinese government has paid attention to upgrading traditional industries through the application of information technology since 1994. Construction industry is one of the focused industries because its scale is increasing due to the rapid economic growth and because the large potential benefit on both economic aspects and on social aspects is expe...