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37 Classification of Software Functionalities Transportation Modeling Categories analytical and deterministic. Analytical and determinis- tic tools are usually based on the procedures found in the Highway Capacity Manual. The resulting factors from these tools, such as capacity, density, Levels of Service (LOS), delay, and queue, are based on empirical equations derived from field data and small-scale exper- iments. This type of tool is able to analyze small-scale effects, but it is not practical for large-scale, network applications. simulation: macroscopic. Macroscopic simulation models use the fundamental traffic qualities of speed, volume, and density on a sectional basis (i.e., network links), which means that tracking individual cars in a macroscopic model is impossible. They require less detailed network link data to operate than microscopic models, but they do not offer as much detail. simulation: mesoscopic. Mesoscopic simulation models pro- vide middle ground between the macro- and microscopic approaches. Mesoscopic models typically are able to track individual vehicles, but they also rely on speed, volume, and density relationships to determine the movement of these vehicles. simulation: microscopic. Microscopic simulation models are capable of tracking individual vehicles on a second- by-second basis and capture the ways that these vehicles interact with each other. This means that these models employ car-following and lane-changing algorithms to determine individual vehicle behaviors. (simulation) tool suite. A tool suite is a computer software package that combines two or three of the simulation types previously described. In this way, a user is able to easily model a network with different fidelities when necessary. Examples include VISSIM with VISUM and TransCAD with TransModeler. ⢠Corridor (pipe) work zone. A corridor work zone (or pipe work zone) is any road work that occurs along a major highway segment. An example of this type of work zone would be an interstate widening or repaving project. This type of work zone is slightly larger in size and has the potential to cause more traffic disruption on the regional level. ⢠Isolated work zone. An isolated work zone can be thought of as a single point within a much larger net- work. Examples of isolated work zones can include rural lane closures or redesigned intersections. This type of work zone is small in size and should have mini- mal impact on traffic over the regional network. ⢠Network (grid) work zone. A network work zone (or grid work zone) is any project that involves construction on connected, interdependent roads with multiple access points. This type of construction may also require one or more viable alternate routes. Examples include interstate reconstruction, full roadway closures, and work zones in urban centers. This type of work zone is large and will disrupt traffic patterns on a large scale. However, the impact is usually restricted to an urban area. ⢠Regional work zone. A regional work zone is similar to a network work zone in that it involves construction on connected and interdependent routes and may require detours. The difference between the two is the size of the traffic impacts. Regional work zones will cause regional- level traffic impacts, which could mean disrupting several urban areas or several towns in a region. sketch planning. Sketch-planning tools provide a rough esti- mate of the effects of any transportation improvements. They typically require only very basic information, such as traffic counts and capacity analysis. Glossary
38 traffic signal optimization. Traffic signal optimization soft- ware packages are tools used to develop signal-timing plans at both isolated locations and synchronized corri- dors or grids. These tools also require basic information such as traffic counts for intersections. travel demand model. Travel demand models are mathemat- ical models used to determine the travel patterns based on demand. Originally, these types of models were developed to determine the impact of infrastructure improvements. They forecast specific outputs, such as mode choice, desti- nation choice, and route choice. Functionality construction management. Construction management involves the overall planning, coordination, determina- tion of resource requirements, and implementation of the project. Determination of time-of-day for construction, project design and optimal construction scheduling, and traffic impact analysis are considered as part of the analy- sis to estimate the impact of management strategies. logistics. Logistics involves determining efficient practices to transport materials and optimal scheduling to reduce operational and storage costs. The work zone logistics involve determining the duration of the closure of lanes, construction techniques, and how the workers will put up the cones, etc. operations. Operations involve analysis of current man- agement and safety of traffic and other users. Operations typically involve planning and maintaining signs, signals, pavement markings, and lighting. The management of intelligent transportation systems and safety initiatives to improve driver behavior are considered. Determination of traffic measurements such as delay, speed, occupancy, lev- els of service, queue lengths, and others are used to evalu- ate the behavior and functionality of traffic operations and management. planning. Planning involves making long-term decisions and goals. The involvement of all users of the system is normally considered as part of the process, as improvement strategies are evaluated to improve the overall functionality of the system. Forecasting of future demand growth, employment, and land use are normally considered, as well as estimating impacts of proposed future improvements. Users and Proprietary Issues engineers. Use by engineers typically involves studying traffic impacts from an operational aspect, as well as the planning process of project-specific construction and operational management strategies. Project design and coordination are topics considered by the engineers interested in actual implementation of such strategies. planners. Use by planners typically involves the advanced long-term planning of strategies of a road network depict- ing various projects to improve systemwide functionality. Demand forecasting, employment, and land use strategies are topics of interest for such planners, as well as system effects and air quality issues based upon traffic and popu- lation growth. proprietary. Proprietary software is defined as software that is licensed under exclusive legal right of the developer and/or owner. The user is given the right to use the soft- ware under license agreements and restricted from tam- pering and modifying such software. Other software may be termed as open source or freeware, meaning the use and licensing is more liberal in use, study, and changes and improvements of software to users. Freeware refers more to the free use of software, while open source is focused on the community use and development of software to benefit the overall software community. Data Inputs cost of various strategies. Different construction strategies have different implications on life-cycle costs. Use of fast construction material and techniques can result in reduc- tion in the period of time work zones are implemented but may require higher regular maintenance costs during the life cycle of the project. These costs and benefits need to be evaluated at a life-cycle level. pavement. As identified in the interviews in the earlier tasks, the pavement management systems of most DOTs and MPOs play a critical role in determining projects and proj- ect sequencing. Therefore, it is critical to determine software tools that require pavement inputs and how they are utilized. production rate for various strategies. Several construc- tion strategies identified during the interviews have dif- ferent production rates depending on the materials being used, the construction technique, weather, and night ver- sus day, all of which have a significant effect on the dura- tion of work zone. traffic. Traffic data include volume counts, speeds, travel time, and density and are used to calibrate and validate simulation models. Dynamic Demand Changes departure time choice. Departure time choice is usually a facet of the mode choice a traveler must make. For instance, a traveler using a passenger car may depart at any time, while a traveler using bus transit must wait until the next bus arrives in order to depart. destination change. A destination change occurs when a traveler diverts to a destination other than the one origi- nally intended when the trip began.
39 en route diversion. A diversion that occurs when a traveler decides to alter his or her route during the trip, because of a number of factors including ITS signs warning of impend- ing congestion, radio announcements, word-of-mouth, or approaching traffic congestion first-hand. induced or foregone demand. Induced demand (latent demand) is a phenomenon that occurs when traffic vol- umes increase in reaction to facility Levels of Service (LOS) and/or capacities that increase. Foregone demand is the opposite effect, where facilities with low LOS and/ or capacities experience lower volumes because of traveler hesitancy to use such facilities. mode shift. Any shift a traveler makes in mode in order to complete a trip is an action that could be part of an overall trip plan or due to dissatisfaction with the current mode. pretrip route diversion. This type of diversion occurs when a traveler decides to alter his or her route before the trip begins. Measure of Effectiveness agency cost. A figurative cost is typically a construction- related cost to a government agency (usually the Trans- portation Department) faced by delay in construction and construction costs. environmental impact. The environmental impact is directly related to the amount of emissions that vehicles make during trips. This measure is especially relevant when a large amount of congestion is present. queue length and delay. Queue lengths and delays are used as measures of effectiveness to evaluate the type and level of impact a work zone will have. road user cost. A figurative cost ascribed to all road users who face delays and congestion. This cost represents the negative impact of such road conditions and the road userâs preference to avoid such costs. safety surrogates. Any data set that can act as a surrogate to safety. For example, speed variance, number of lane changes, and conflicting points are all considered safety surrogates. traffic conditions. Traffic conditions represent a broad data set used by traffic engineers and planners to assess the traffic conditions (e.g., speed, delays, accelerations, lane changing) on any particular roadway. Resource Requirements animation or presentation. The ability of the software to make animations or presentations is very important for traffic simulation to present results and also to locate trou- ble spots in the network. availability of source code or algorithm. Open source soft- ware is any computer program that allows fellow devel- opers to see the actual code that makes up the software. This makes it much easier for developers in similar areas to calibrate. Open source software is usually free or donation-based. computational speed. The computational speed of software is a measure of the amount of time it takes to execute all the required steps from start to finish. Most can be done in a matter of minutes, but more complicated systems can take several hours. cost. The cost of software is the price that the developer and/ or publisher ask the user to pay for their product. This is the opposite of nonproprietary software, which is avail- able for free or by donation. effort in application. The amount of effort required in transferring an existing network or data set into the newer system. Excel based. Excel-based software uses Microsoft Excel as a window into which the software is entered. This means that the software is merely an extension of Excel, rather than unique software. level of effort for training. This is a measure of the soft- wareâs ease of use. Easy software can be understood after only a few demonstrations, but more complicated soft- ware may require several days of training. As a general rule, open source software is usually more complex and less user-friendly than commercially developed software. memory. The amount of memory a given program will take up is a measure of the size (in bytes) of the program and its files. transferability of data to other packages. The ability of data to be exchanged across multiple packages is impor- tant in order to coordinate output between packages. This is usually facilitated by either converting the file or relying on a universal file format. Strategies Based on the literature review and interviews conducted, the team identified several work zone strategies to minimize impact. Software tools were evaluated based on whether they have the ability to evaluate the following strategies: ⢠Constructability versus project delivery; ⢠Daytimeânighttime work; ⢠Early and late dynamic merging; ⢠Grouping nontraffic tasks; ⢠Improve parallel roads; ⢠Improve signal timing; ⢠Incentive/disincentive; ⢠Pavement programming; ⢠Programming by element; ⢠Scheduling under critical events or sensitive land use; ⢠Short-duration closures; ⢠Total versus partial shutdown; ⢠Work zone ITS; and ⢠Work zone speed management.
