Transportation Engineering and Its Development PDF

Transportation Engineering and Its Development Introduction to Transportation Definition o Movement of humans, animals, and goods from one location to another. Logistics Role o Determines efficiency in moving products to meet consumer needs. Importance...

Transportation Engineering and Its Development Introduction to Transportation Definition o Movement of humans, animals, and goods from one location to another. Logistics Role o Determines efficiency in moving products to meet consumer needs. Importance o Integral to modern life; must be affordable, flexible, and sustainable. Introduction to Transportation Engineering  Definition o Branch of civil engineering focused on planning, design, construction, and operation of transportation systems. Responsibilities o Ensure safety, comfort, convenience, and environmental compatibility. Traffic Engineering o Focuses on planning and operations of roads, streets, and highways. History of Transportation Wheel on Carts (3500 BC) o First use for transportation on Mesopotamian chariots. River Boat (3500 BC) o Designed for inland navigation. Flying Machines (1492) o Theories by Leonardo da Vinci. Horses (2000 BC) o Evidence from chariot burials. Submarine (1620) o First human-oared submersible by Cornelis Drebbel. Public Bus (1662) o First horse-drawn bus with a regular route and fare system. Paddle Wheel Steamboat (1783) o Powered by steam engines. Hot Air Balloon (1783) o First successful human-carrying flight technology. STEAMBOAT (1787) o A boat that is propelled primarily by steam power. IMPORTANCE OF TRANSPORTATION To transfer messages and information. Without well- developed transportation systems, logistics could not bring its advantages into full play. It facilitates trade, exchange and travels. It prevents regions to be largely isolated with each other. It allows people to move to new areas. It allows people to get to their destination. MAIN COMPONENTS OF TRANSPORTATION SYSTEM  Infrastructure Vehicles Control systems and technology Operators Users: DIFFERENT MODES OF TRANSPORTATION IN THE DEVELOPMENT OF THE OTHER COUNTRY Road Transport - it is relatively cheaper mode of transport as compared to other modes. - perishable goods can be transported at a faster speed by road carries over a short distance. Water Transport - it is relatively economical mode of transport for bulky and heavy goods. - it is a safe mode of transport with respect to occurrence of accidents. - it promotes international trades. Air Transport - it is the most safest and convenient mode of transport during natural calamities. - it is very useful in transporting goods and passengers to the area, which is not accessible by any other means. - it provides vital support to the national security and defense Rail Transport - it is a convenient mode of transport for travelling long distances. - its operation is less affected by adverse weather conditions like rain, floods, fogs, etc. CABLE TRANSPORT MARITIME TRANSPORT PIPELINES TRANSPORT Transit modes Transit modes refer to the various systems used to move passengers within a public transportation network. These modes can include: Mass transit is characterized by fixed routes, published schedules designated networks, and specified stops. Mass-transit vehiclesinclude buses, light rail (trolleys), or rapid transit systems that either share space in mixed traffic or operate on grade separated rights-of-way. Paratransit is characterized by flexible and personalized service intended to replace conventional fixed-route, fixed-schedule mass-transit lines. Paratransit is available to the public on demand, by subscription, or on a shared-ride basis. Examples include taxi, car rental, dial-a-ride, and specialized services for elderly, medical, and other designated users. Ridesharing (as the name implies) is characterized by two or more persons traveling together by prearrangement, such as carpool, vanpool, or shared-ride taxi. Public Transportation Public transportation is a generic term used to describe the family of transit services available to urban and rural residents. Thus, it is not a single mode but a variety of traditional and innovative services, which should complement each other to provide system-wide mobility. The role and Future of public transportation Public transportation is an important element of the total transportation services provided within large and small metropolitan areas. A major advantage of public transportation is that it can provide high-capacity, energy-efficient movement in densely traveled corridors. It also serves medium- and low-density areas by offering an option for auto owners who do not wish to drive and an essential service to those without access to automobiles, such as school children, senior citizens,single-auto families, and others who may be economically or physically disadvantaged. Summary The transportation system in a developed nation consists of a network of modes that have evolved over many years. The system consists of vehicles, guideways, terminal facilities, and control systems; these operate according to established procedures and schedules in the air, on land, and on water. The system also requires interaction with the user, the operator, and the environment. The systems that are in place reflect the multitude of decisions made by shippers, carriers, government, individual travelers, and affected nonusers concerning the investment in or the use of transportation. The transportation system that has evolved has produced a variety of modes that complement each other. Intercity passenger travel often involves auto and air modes; intercity freight travel involvespipeline, water, rail, and trucking. Urban passenger travel involvesauto or public transit; urban freight is primarily by truck. Week 2: Highway Transportation System Highway Transportation System (HTS) The Highway Transportation System is considered the most complex system of transportation and is designed to enable people and goods to move from place to place as safely and efficiently as possible. Three Main Parts of HTS Roadways Types of roads – Interstates, Country, Residential, City, and Business are all example of different types of roads. Features – a curve, a guardrail, a shoulder, streetlights, or intersections are all example of different features of roads. Surfaces – asphalt, concrete, dirt, snow covered, wet from rain, or covered by wet leaves are all example of different surfaces. Different Features of Roadways Curves - Road curves are irregular bends in roads to bring a graduation change of direction. Similar curves are on railways and canals. Curves provided in the horizontal plane are known as horizontal curves and are generally circular or parabolic. Curves provided in the vertical plane are known as vertical curve. Guardrail - A guardrail is a longitudinal, roadside barrier system that is installed to prevent errant vehicles from impacting roadside obstacles. Shoulder - A shoulder, hard shoulder (British) or breakdown lane is an emergency stopping lane by the verge of a road or motorway Streetlights - Street lighting is to authorize road users to view accurately and easily the carriageway and the quick surroundings in darkness. Street lighting enhances visibility at night through artificial lighting decreases stress on driving and makes sure comfort. It feels very easy to drive a vehicle in the presence of street lighting. Intersection - An intersection or an at-grade junction is a junction where two or more roads converge, diverge, meet or cross at the same height, as opposed to an interchange, which uses bridges or tunnels to separate different roads. Different Surfaces of Roadways Asphalt - Asphalt concrete (commonly called asphalt, blacktop, or pavement in North America, and tarmac or bitumen macadam in the United Kingdom and the Republic of Ireland) is a composite material commonly used to surface roads, parking lots, airports, and the core of embankment dams. Asphalt mixtures have been used in pavement construction since the beginning of the twentieth century. Concrete - Concrete surfaces (specifically, Portland cement concrete) are created using a concrete mix of Portland cement, coarse aggregate, sand, and water. In virtually all modern mixes there will also be various admixtures added to increase workability, reduce the required amount of water, mitigate harmful chemical reactions, and for other beneficial purposes. Dirt - A dirt road or track is a type of unpaved road not paved with asphalt, concrete, brick, or stone; made from the native material of the land surface through which it passes, known to highway engineers as subgrade material. Snow Covered - A snow road is a type of winter road, which is a road that is used or trafficable only in the winter. Snow roads make up some or all of the on-land segments of a winter road. Vehicles ⚫ Bicycles ⚫ Motorcycles ⚫ Animal Drawn Vehicles ⚫ Cars ⚫ SUV’s ⚫ Trucks ⚫ Tractor-Trailers ⚫ Emergency Vehicles Vehicles Features – Airbags, Seatbelts, anti-locking braking system, GPS, Electronic stabilization system, auto stick and all wheel drive are all examples of different types of features a vehicle may possess. Performance Capabilities – Turning radii (how well can your vehicle turn), stopping distances, and crash test rating are all examples of different types of performance capabilities vehicles are measured by. Users Drivers – age, experience, values, emotions, habits, health, and handicaps are all example that make drivers the most critical aspect of Highway Transportation System. Pedestrians – a construction worker or crew, a police officer directing traffic, a jogger wearing headphones, a child playing in their driveway, and a blind person crossing the street are all examples of elements that make the category, pedestrians. Animals – a deer, squirrels, dogs, cats, birds or any other animal that may cross the path of a driver. Designing Good Highways Early American Roads were built along trails. Most were giving little or no thought of the future. Now engineers are carefully designing and thinking of routes that best fit everyone’s needs. Federal and State Requirements National Traffic and Motor Vehicle Safety Act Automakers are required to build certain safety features, such as safety belts and shatterproof windows, into their motor vehicles. National Highway Safety Act Guidelines: Vehicle registration, Driver Licensing, Traffic Laws, Traffic Courts, Highway Construction and Maintenance. Each state sets its own statutes or laws, that concern highway safety. Reducing Your Risk Within the HTS ⚫ Keep your vehicle in top condition ⚫ Anticipate the actions of others ⚫ Take steps to protect yourself and others ⚫ Drive only when you are in sound physical and mental condition ⚫ Make a conscious effort to develop your driving skills The IPDE Process Identify Identify objects or conditions within 12 to 15 seconds ahead that could interfere with your planned path of travel. To aid in this process, a driver must practice scanning the driving environment for the primary purpose of IDENTIFYING real and potential hazards, e.g., an oncoming vehicle in your lane of travel or a child playing near the roadway, respectively. -Open Closed Zones -Traffic Controls -Roadway features and conditions -Other users -Specific Clues Predict The second step in the IPDE method is to PREDICT what might happen should you encounter a real or potential hazard. For real hazards, such as an oncoming vehicle that drifts into your lane of travel, simply predict whether the oncoming vehicle will continue toward your car and, if so, what consequences the oncoming car's path of travel might involve. As with any dynamic environment, your prediction process might require a re-assessment if another real hazard is identified between you and the oncoming vehicle — such as a child runs into the street chasing a ball directly in front of your vehicle. Decide This process requires an understanding of the need for necessary time and space to implement the “ decided-upon" vehicle control maneuver. Decide what action(s) to take at least 4 to 5 seconds ahead of time to control or reduce risk. *Decision will be influenced by the speed of own vehicle as well as the speed of other vehicles* -Change or maintain speed -Change directions -Communicate Execute Carry out your decision to avoid conflict is the execute step in the IPDE process. *This step involves the physical skills used in driving.* -Control Speed -Steer -Communicate -Combine Actions The Smith System The Smith System 5 Keys is a simple and straightforward system that allows you to avoid making costly mistakes on the road. 1. Aim High and Look Ahead Look way ahead of your vehicle (20 to 30 seconds ahead), not down at the road directly in front of you. 2. Keep Your Eyes Moving Search the scene constantly for changes that might require you to adjust your speed or position. 3. Get the Big Picture Search the whole scene, not just part of it. 4. Make Sure Others See You Communicate with drivers and pedestrians. 5. Leave Yourself a Way Out Always leave yourself a path of escape (a way to avoid a collision) How Vision Affects Your Ability to Drive Visual Acuity – clear vision Field of Vision Central Vision – the narrow cone-shaped area directly in front of you Peripheral Vision – angles to your right and left Vertical Field of Vision – up and down Depth Perception – gives a 3-dimensional perspective to objects (distance judgment) Week 3: Transportation Planning, Urban Transportation Planning TRANSPORTATION PLANNING Transport planning is defined as planning required in the operation, provision and management of facilities and services for the modes of transport to achieve safer, faster, comfortable, convenient, economical and environment-friendly movement of people and goods. The purpose of transportation planning is for transportation professionals to make them able to estimate traffic patterns in the form of traffic volumes on various facilities. This information is useful in determining how to design the facility, how to operate the facility, and what improvements might be most useful in the long term to manage the demand for transportation. The process must be flexible enough to be applicable to any transportation project or system, because the kinds of problems that transportation engineers work on will vary over time. Transportation has undergone considerable change in emphasis over a 200-year period; such modes as canals, railroads, highways, air, and public transit have each been dominant at one time or another. Thus, the activities of transportation engineers have varied considerably during this period, depending on society’s needs and concerns. Examples of changing societal concerns include energy conservation, traffic congestion, environmental impacts, safety, security, efficiency, productivity, and community preservation. The transportation planning process is not intended to furnish a decision or to give a single result that must be followed, although it can do so in relatively simple situations. Rather, the process is intended to provide the appropriate information to those who will be affected and those responsible for deciding whether the transportation project should go forward. PURPOSE OF TRANSPORTATION PLANNING ⚫ Identifying multiple options for transportation ⚫ Identifying outlying problems to a transportation system ⚫ Identifying possible solutions to those identified transportation system ⚫ Optimization of existing transportation systems and structural design IMPORTANCE OF TRANSPORTATION PLANNING Obsolete road designs, roadside hazards, and substandard road conditions can cause highway fatalities in different areas of the country. Effective transport in urban areas is essential to the accessibility of land, growth of the economy, and the overall environment of the city. These hazards should be routinely monitored and fixed for the betterment of the people. PLANNING PROCESS The transportation planning process comprises seven basic elements, which are interrelated and not necessarily carried out sequentially. The information acquired in one phase of the process may be helpful in some earlier or later phase, so there is a continuity of effort that should eventually result in a decision. The elements in the process are: Situation definition Problem definition Search for solutions Analysis of performance Evaluation of alternatives Choice of project Specification and construction Situation Definition Involves all of the activities required to understand the situation that gave rise to the perceived need for a transportation improvement In this phase, the basic factors that created the present situation are described, and the scope of the system to be studied is delineated. The present system is analyzed and its characteristics are described. Information about the surrounding area, its people, and their travel habits may be obtained. Examples: Inventory transportation facilities Measure travel pattern Review prior studies Problem Definition To describe the problem in terms of objectives to be accomplished by the project and to translate those objectives into criteria that can be quantified. Objectives are statements of purpose such as to reduce traffic congestion, to improve safety in a particular road to maximize net highway-user benefits and; to reduce noise Search for a Solution In this phase of the planning process, consideration is given to variety of ideas, design, location, and system configuration that might provide solution to the problem. This is the brainstorming stage, in which many options may be proposed for later testing and evaluation. Alternatives can be proposed by any group or organization. In fact, the planning study may have been originated to determine the feasibility of a particular project or idea, such as adding bike lanes to reduce traffic volumes. The transportation engineer has a variety of options available in any particular situation, and any or all may be considered in this idea-generating phase. Among the options that might be used are different types of transportation technology or vehicles, various system or network arrangements, and different methods of operation. This phase also includes preliminary feasibility studies, which might narrow the range of choices to those that appear most promising. Some data gathering, field testing, and cost estimating may be necessary at this stage to determine the practicality and financial feasibility of the alternatives being proposed. Analysis of Performance The purpose of performance analysis is to estimate how each of the proposed alternatives would perform under present and future conditions. Included in this step is a determination of the investment cost of building the transportation project, as well as annual costs for maintenance and operation. This element also involves the use of mathematical models for estimating travel demand. The number of persons or vehicles that will use the system is determined, and these results, expressed in vehicles or persons/hour, serve as the basis for project design. Other information about the use of the system (such as trip length, travel by time of day, and vehicle occupancy) are also determined and used in calculating user benefits for various criteria or measures of effectiveness. This task is sometimes referred to as the transportation planning process, but it is really a systems analysis process that integrates system supply on a network with travel demand forecasts to show equilibrium travel flows. Example: For each option or proposed solution, determine the costs of the implementation of the project, how will the traffic flow be affected, and the impact this proposal will have on the consumers. Evaluation of Alternative The purpose of the evaluation phase is to determine how well each alternative will solve the main objectives of the project. The performance data produced in the analysis phase are used to compute the benefits and costs that will result if the project is selected. Example: For a bridge project, determine The benefits of the project versus the costs required to do the project. The profitability of the project from the future consumers. Cost-effectiveness of the project Choice of Project This part of the planning process is made after carefully considering all the factors that may or may not contribute to the project. The transportation engineer, who participates in the planning process, may have developed a strong opinion as to which alternative to select. Such bias could result in the early elimination of promising alternatives or the presentation to decision-makers of inferior projects. Before deciding whether or not to build the proposed bridge, decision-makers look carefully at the revenue-cost forecasts and would likely consider projects that appear to be financially sound. The site location is selected based on a careful study of the factors involved. The information gathered in the earlier phases would be used, together with engineering judgment and political considerations, to arrive at a final project selection. Specification and Construction Once the transportation project has been selected, the project can proceed into the detailed design phase in which each of the components of the facilities is specified. For a transportation facility, this involves its physical location, geometric dimensions, and structural configuration. Design plans are produced that can be used by contractors to estimate the cost of building the project. When a construction firm is selected, these plans will be the basis on which the project will be built. For the bridge project, once a decision to proceed has been made, a design is produced that includes the type of superstructure, piers and foundations, roadway widths and approach treatment, as well as appurtenances such as tollbooths, traffic signals, and lighting. These plans are made available to contractors, who submit bids for the construction of the bridge. If a bid does not exceed the amount of funds available and the contractor is deemed qualified to do the work, the project proceeds to the construction phase. Upon completion, the new bridge is turned over to the local transportation authority for operation and maintenance. URBAN TRANSPORTATION PLANNING Urban transportation planning involves the evaluation and selection of highway or transit facilities to serve present and future land uses. For example, the construction of a new shopping center, airport, or convention center will require additional transportation services. Also, new residential development, office space, and industrial parks will generate additional traffic, requiring the creation or expansion of roads and transit services. The process must also consider other proposed developments and improvements that will occur within the planning period. The urban transportation planning process has been enhanced through the efforts of the Federal Highway Administration and the Federal Transit Administration of the U.S. Department of Transportation by the preparation of manuals and computer programs that assist in organizing data and forecasting travel flows. Urban transportation planning is concerned with two separate time horizons. The first is a short-term emphasis intended to select projects that can be implemented within a one- to three-year period. These projects are designed to provide better management of existing facilities by making them as efficient as possible. The second time horizon deals with the long-range transportation needs of an area and identifies the projects to be constructed over a 20-year period. SHORT TERM This type of planning pertains to different matters regarding transportation within a certain area that can be accomplished within three (3) years. These projects are designed to provide better management of existing facilities by making them as efficient as possible. Short-term projects involve programs such as traffic signal timing to improve flow, car and van pooling to reduce congestion, park-and-ride fringe parking lots to increase transit ridership, and transit improvements. LONG TERM This type of planning is more structured and complex. It requires thorough inspection and planning better than short term planning. This type of planning usually is accomplished with five (5) or more years. Long-term projects involve programs such as adding new highway elements, additional bus lines or freeway lanes, rapid transit systems and extensions, or access roads to airports or shopping malls. Establishment of Goals and Objectives The urban transportation study is carried out to develop a program of highway and transit projects that should be completed in the future. Thus, a statement of goals, objectives, and standards is prepared that identifies deficiencies in the existing system, desired improvements, and what is to be achieved by the transportation improvements. Example: if a transit authority is considering the possibility of extending an existing rail line into a newly developed area of the city, its objectives for the new service might be to maximize its revenue from operations, maximize ridership, promote development, and attract the largest number of auto users so as to relieve traffic congestion. Generation of Alternatives In this phase of the urban transportation planning process, the alternatives to be analyzed will be identified. It also may be necessary to analyze the travel effects of different land-use plans and to consider various lifestyle scenarios. The options available to the urban transportation planner include various technologies, network configurations, vehicles, operating policies, and organizational arrangements. Estimation of Project Cost and Travel Demand This activity in the urban transportation planning process involves two separate tasks. The first is to determine the project cost, and the second is to estimate the amount of traffic expected in the future. The estimation of facility cost is relatively straightforward, whereas the estimation of future traffic flows is a complex undertaking requiring the use of mathematical models and computers. Evaluation of Alternatives This phase of the process is similar in concept to what was described earlier but can be complex in practice because of the conflicting objectives and diverse groups that will be affected by an urban transportation project. The purpose of the evaluation process is to identify feasible alternatives in terms of cost and traffic capacity, to estimate the effects of each alternative in terms of the objectives expressed, and to assist in identifying those alternatives that will serve the traveling public and be acceptable to the community. Of particular importance are the environmental assessments mandated in most urban transportation studies. Choice of Project Selection of a project will be based on a process that will ultimately involve elected officials and the public. Quite often, funds to build an urban transportation project (such as a subway system) may involve a public referendum. In other cases, a vote by a state legislature may be required before funds are committed. A multiyear program then will be produced that outlines the projects to be carried out over the next 20 years. With approval in hand, the project can proceed to the specification and construction phase. Summary Transportation projects are selected based on a variety of factors and considerations. The transportation planning process is useful when it can assist decision makers and others in the community to select a course of action for improving transportation services. Week 4: Forecasting Travel Demands, trip generation and distribution Forecasting travel demand -Is a key component of the transportation engineer’s technical repertoire. It allows the engineer to predict the volume of traffic that will use a given transportation element in the future, whether that element is an existing highway or a potential-rail route. Four-Step Travel Demand Model ⚫ Originally developed in the 1950’s and 1960’s when planning major highway facilities ⚫ Four decisions are the basis of the traditional travel demand model: ⚫ The choice and reason to travel ⚫ The destination to travel ⚫ The mode by which to travel ⚫ The route on which to travel Forecasting travel demands Divided process into 4 steps: ⚫ Trip Generation ⚫ Trip Distribution ⚫ Mode Split ⚫ Trip Assignment ⚫ Trip generation and distribution Trip generation -is the first stage of the classical first generation aggregate demand models. -it aims at predicting the total number of trips generated and attracted to each zone of the study area. -in other words this stage answers the questions to “how many trips” originate at each zone. Trip purpose Work School Serving passengers (picking up and dropping off). Recreational – Social Shopping Factors affecting Trip Generation ⚫ Income ⚫ Car ownership ⚫ Family size and composition ⚫ Land use characteristics ⚫ Distance of zone from the town center ⚫ Accessibility to public transport system and its efficiency ⚫ Employment opportunities Growth factor modeling Growth factor modes tries to predict the number of trips produced or attracted by a house hold or zone as a linear function of explanatory variables. The models have the following basic equation: Ti = fi x ti Where: Ti = The number of future trips in the zone fi = Growth factor ti = The number of current trips in that zone (trip/day) The growth factor fi depends on the explanatory variable such as population (P) of the zone , average house hold income (I) , average vehicle ownership (V). The simplest form of fi is represented as follows where the subscript ” d” denotes the design year and the subscript ”c” denotes the current year. Growth factor modeling Example Given that a zone has 275 household with car and 275 household without car and the average trip generation rates for each groups is respectively 5.0 and 2.5 trips per day. Assuming that in the future, all household will have a car, find the growth factor and future trips from that zone, assuming that the population and income remains constant. Solution: Current trip rate ti = (275 × 5.0) + (275 × 2.5) = 2062.5 trips / day. Growth factor fi = Vi^d/Vi^c = 550/275=2.0 Therefore, no. of future trips Ti = fi x ti = 2.0 × 2062.5 = 4125 trips / day. Trip distribution -is a model of the number of trips that occur between each origin zone and each destination zone. -these models try to mathematically describe the destination-choice phase of the sequential demand analysis procedure. -it uses the predicted number of trips originating in each origin zone (trip production model) and the predicted number of trips ending in each destination zone (trip attraction model). Factors which affect the number of trips between two zones: ⚫ The number of trips produced by the origin zone. ⚫ The degree to which the in-site attributes of the destination zone attract trip makers. ⚫ The factors that inhibit travel between a pair of zones. Growth factor methods Trip matrix The trip pattern in a study area can be represented by means of a trip matrix or origin-destination (O- D)matrix. This is a two dimensional array of cells where rows and columns represent each of the zones in the study area. The notation of the trip matrix is given in figure The cells of each row i contain the trips originating in that zone which have as destinations the zones in the corresponding columns. Tij is the number of trips between origin i and destination j. Oi is the total number of trips between originating in zone i and Dj is the total number of trips attracted to zone j. The sum of the trips in a row should be equal to the total number of trips emanating from that zone. The sum of the trips in a column is the number of trips attracted to that zone. These two constraints can be represented as: ΣjTij = Oi ΣiTij = Dj If reliable information is available to estimate both Oi and Dj, the model is said to be doubly constrained. In some cases, there will be information about only one of these constraints, the model is called singly constrained. Uniform growth factor If the only information available is about a general growth rate for the whole of the study area, then we can only assume that it will apply to each cell in the matrix, that is a uniform growth rate. The equation can be written as: Tij = f × tij where f is the uniform growth factor tij is the previous total number of trips, Tij is the expanded total number of trips. Advantages are that they are simple to understand, and they are useful for short-term planning. Limitation is that the same growth factor is assumed for all zones as well as attractions. Example Trips originating from zone 1,2,3 of a study area are 78,92 and 82 respectively and those terminating at zones 1,2,3 are given as 88,96 and 78 respectively. If the growth factor is 1.3 and the cost matrix is as shown below, find the expanded origin-constrained growth trip table. Solution: Given growth factor = 1.3, Therefore, multiplying the growth factor with each of the cells in the matrix gives the solution as shown below. Mode Choice Mode choice is that aspect of the demand analysis process that determines the number (or percentage) of trips between zones that are made by automobile and by transit. The selection of one mode or another is a complex process that depends on factors such as the traveler’s income, the availability of transit service or auto ownership, and the relative advantages of each mode in terms of travel time, cost, comfort, convenience, and safety. Final Assignment The final step in the transportation forecasting process is to determine the actual street and highway routes that will be used and the number of automobiles and buses that can be expected on each highway segment. To carry out a trip assignment, the following data are required: (1) number of trips that will be made from one zone to another (this information was determined in the trip distribution phase), (2) available highway or transit routes between zones, (3) how long it will take to travel on each route, (4) a decision rule (or algorithm) that explains how motorists or transit users select a route, and (5) external trips that were not considered in the previous trip generation and distribution steps. Summary The process of forecasting travel demand is necessary to determine the number of persons or vehicles that will use a new transportation system or component. The methods used to forecast demand include extrapolation of past trends, elasticity of demand, and relating travel demand to socioeconomic variables. Urban travel demand forecasting is a complex process, because demand for urban travel is influenced by the location and intensity of land use; the socioeconomic characteristics of the population; and the extent, cost, and quality of transportation services. Travel demand forecasts are also required for completing an economic evaluation of various system alternatives. Highway Transportation System (HTS) Definition o Complex system designed for safe and efficient movement of people and goods. Main Parts o Roadways ▪ Types: Interstates, Country, Residential, City, Business.  ▪ Features: Curves, guardrails, shoulders, streetlights, intersections. ▪ Surfaces: Asphalt, concrete, dirt, snow-covered. Vehicles in HTS Types of Vehicles o Bicycles, motorcycles, animal-drawn vehicles, cars, SUVs, trucks, emergency vehicles. Features o Safety features (airbags, seatbelts), performance capabilities (turning radii, stopping distances). Designing Good Highways Historical Context o Early roads built along trails with little foresight. Modern Approach o Engineers design routes considering future needs. Safety Regulations o National Traffic and Motor Vehicle Safety Act and National Highway Safety Act. The IPDE Process Identify o Recognize potential hazards within 12-15 seconds. Predict o Anticipate outcomes of hazards. Decide o Determine actions to take. Execute o Carry out the decision to avoid conflict. The Smith System Five Keys o Aim high and look ahead. o Keep your eyes moving. o Get the big picture. o Make sure others see you. o Leave yourself a way out. Importance of Transportation Functions o Transfers messages, facilitates trade, prevents isolation, allows mobility.  Components of Transportation System o Infrastructure, vehicles, control systems, operators, users. Modes of Transportation o Road, water, air, rail, maritime, cable, pipelines. Transportation Planning Definition o Planning for safe, efficient, and environmentally friendly transport. Purpose o Estimate traffic patterns and design facilities. Planning Process o Situation definition, problem definition, search for solutions, analysis of performance, evaluation of alternatives, choice of project, specification and construction. Urban Transportation Planning Focus o Evaluate and select facilities for current and future land uses. Time Horizons o Short-term (1-3 years) and long-term (20 years). Goals and Objectives o Identify deficiencies and desired improvements. Forecasting Travel Demand Importance o Predicts traffic volume for existing and potential transportation elements. Four-Step Travel Demand Model o Trip generation, trip distribution, mode split, trip assignment. Factors Affecting Trip Generation o Income, car ownership, family size, land use, accessibility. Mode Choice o Determined by income, transit availability, travel time, cost, and safety.