Reduced Clearance Time Research Articles

Influence of road network and population demand assumptions in evacuation modeling for distant tsunamis

Tsunami evacuation planning in coastal communities is typically focused on local events where at-risk individuals must move on foot in a matter of minutes to safety. Less attention has been placed on distant tsunamis, where evacuations unfold over several hours, are often dominated by vehicle use and are managed by public safety officials. Traditional traffic simulation models focus on estimating clearance times but often overlook the influence of varying population demand, alternative modes, background traffic, shadow evacuation, and traffic management alternatives. These factors are especially important for island communities with limited egress options to safety. We use the coastal community of Balboa Island, California (USA), as a case study to explore the range of potential clearance times prior to wave arrival for a distant tsunami scenario. We use a first-in–first-out queuing simulation environment to estimate variations in clearance times, given varying assumptions of the evacuating population (demand) and the road network over which they evacuate (supply). Results suggest clearance times are less than wave arrival times for a distant tsunami, except when we assume maximum vehicle usage for residents, employees, and tourists for a weekend scenario. A two-lane bridge to the mainland was the primary traffic bottleneck, thereby minimizing the effect of departure times, shadow evacuations, background traffic, boat-based evacuations, and traffic light timing on overall community clearance time. Reducing vehicular demand generally reduced clearance time, whereas improvements to road capacity had mixed results. Finally, failure to recognize non-residential employee and tourist populations in the vehicle demand substantially underestimated clearance time.

Comparison of venturi and peristaltic vacuum in phacoemulsification

To evaluate the efficiency of peristaltic-based and venturi-based vacuums. John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. Experimental study. Porcine lenses were hardened with formalin and cut into 2.0 mm cubes. Time to fragment removal (efficiency) and fragment bounces off the tip (chatter) were measured using a Signature machine with the ability to switch between peristaltic-based and venturi-based vacuum. Micropulse longitudinal and transversal ultrasound motions were tested. Venturi-based vacuum had increased efficiency and decreased chatter compared with peristaltic-based vacuum at lower vacuum levels. Use of a venturi-based vacuum, when available, may result in reduced clearance time of lens material and mitigate chatter even under noisy conditions. No author has a financial or proprietary interest in any material or method mentioned.

A Scenario-based Model for Fleet Allocation of Freeway Service Patrols

As one component of traffic incident management systems, freeway service patrols (FSP) facilitate quick removal of incidents through faster response and reduced clearance time. This paper is to investigate how to strategically allocate tow trucks among patrol beats to optimize the performance of the FSP system. A mixed-integer nonlinear programming model is formulated to minimize the expected loss with respect to a set of high-consequence scenarios of incident occurrence, which may be solved in polynomial time for realistic networks. Moreover, the data required for the model can be easily obtained from practice.

Optimal Fleet Allocation of Freeway Service Patrols

As one component of traffic incident management systems, freeway service patrols (FSP) facilitate quick removal of incidents through faster response and reduced clearance time. This paper is to investigate how to allocate tow trucks among patrol beats to maximize the effectiveness of the FSP services. A min–max bi-level programming model is proposed to determine an optimal fleet allocation that minimizes the maximal system travel time that incidents may incur. A heuristic iterative solution algorithm is proposed to solve the model. Both the model and the algorithm are demonstrated and validated through a numerical example.

Heuristic Priority Ranking of Emergency Evacuation Staging to Reduce Clearance Time

Hazardous events, both natural and human-made, present tremendous risks to communities throughout the world. These events typically necessitate the evacuation of local or regional populations to safe destinations or shelters and have warning times ranging from minutes to hours or even days. The size and scope of these events present a challenge to the emergency management or agency personnel who must see to the health and safety of those living or working in their jurisdiction. This study evaluated various heuristic strategies to improve evacuation of an at-risk region by using a representative traffic roadway network. Finding evacuation strategies that reduce clearance time would lead to saving lives, time, and money. For the given test network, population density, or total number of trips, has an effect on overall clearance times; as densities (trips) increase, a greater potential for improved clearance time is indicated. Six different shift strategies were evaluated, each strategy based on origin-to-destination distances. For departure volumes greater than five vehicles per acre (approximately 12 vehicles per hectare), clearance times showed statistically significant improvements when departure times were shifted for groups within the network. In addition, the amount of the departure shift has an effect on clearance time.

Heuristic Priority Ranking of Emergency Evacuation Staging to Reduce Clearance Time

Hazardous events, both natural and human-made, present tremendous risks to communities throughout the world. These events typically necessitate the evacuation of local or regional populations to safe destinations or shelters and have warning times ranging from minutes to hours or even days. The size and scope of these events present a challenge to the emergency management or agency personnel who must see to the health and safety of those living or working in their jurisdiction. This study evaluated various heuristic strategies to improve evacuation of an at-risk region by using a representative traffic roadway network. Finding evacuation strategies that reduce clearance time would lead to saving lives, time, and money. For the given test network, population density, or total number of trips, has an effect on overall clearance times; as densities (trips) increase, a greater potential for improved clearance time is indicated. Six different shift strategies were evaluated, each strategy based on origin-to-de...

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