Emme Transport Modelling Technology

Emme provides a uniquely flexible, open approach to modelling that allows users the freedom to leverage established techniques or create new methods to address local needs. Modellers and planners have relied on Emme for over two decades, and today Emme powers some of the world's most sophisticated transport planning models.

The Emme Core Modelling Framework

• Private Transport – Traffic Assignment, Path Analysis
• Public Transport – Transit Assignment, Strategy Analysis
• Demand Modelling – Matrix Calculators, Matrix Balancing Procedures
• Analysis and Automation – Network Calculators, Automation Framework

The Emme Core modelling framework offers unrivaled flexibility to address local concerns, and provides modellers opportunities to extend and innovate. The Emme Core is a toolkit of modules designed to facilitate the discovery and development of transport planning models.

The Emme Core offers the planner a complete and comprehensive set of tools for demand modelling, multimodal network modelling and analysis, and for the implementation of evaluation procedures.

Traffic Assignment. Emme offers three best-in-class traffic assignments. Whichever you choose, you'll appreciate the efficiency and reliability that Emme users count on.

• Standard Traffic Assignment. User-optimal Frank and Wolfe equilibrium traffic assignment using linear approximation.
• Parallel Standard Traffic Assignment. Parallel computing version of the Standard Traffic Assignment, offering speedups on multiprocessor systems.
• Path-based Traffic Assignment. Fast-converging new user-optimal equilibrium traffic assignment offering dramatic performance improvements, better convergence, and faster analysis of path-based results, as well as warm starts for faster iterations in feedback.

The user-optimal equilibrium assignments provided by all Emme traffic assignments are designed to be used either directly, or as building blocks with which users are free to implement countless variations. Implement rudimentary all-or-nothing and incremental assignments, or more sophisticated procedures including system-optimal assignments, stochastic user-equilibrium assignments, asymmetric cost assignment for turn-delay applications, or even multiclass assignments where per-class link costs depend on factors such as average speed or vehicle class mix (for example, cars and trucks).

Each of the Emme traffic assignment procedures provides link- and turn-travel costs (volume-delay functions and turn-penalty functions, respectively) as open, user-configurable algebraic expressions. This allows modellers to apply any cost formulation without software updates or add-on software modules. Generalized cost formulations let you account for tolls, vehicle operating costs, carbon fees, and let you specify background traffic volumes as a surrogate for missing transit vehicles or truck demand, or to layer more complex assignment logic.

Multiclass support allows for simultaneous assignment of different vehicle classes characterized by different network perceptions, different network access, or distinct input demand. This further allows for applications like traffic restrictions, carpool/HOV lanes, toll roads, bicycle traffic, areas with restricted access, or privileges by vehicle class, including HEV/LEV (high/low-emissions vehicles).

With the pervasive Emme automation framework, you can take advantage of Emme traffic assignments to implement just about any “feedback” or equilibration method imaginable. The Emme Standard Traffic Assignment includes built-in capabilities for variable demand assignment. The Emme Path-based Traffic Assignment dramatically improves run-times on feedback models by making use of saved paths.

Path Analysis. Each of the Emme traffic assignment tools provides Emme Path Analysis capabilities, allowing select-link and select-turn analyses, skims, partial assignments, and more. Model emissions due to cold starts, vehicles looking for parking space, local vs. regional traffic, ramp-to-ramp matrices, toll matrices, and other applications. Emme’s comprehensive set of path analysis keywords and operators allows for the computation of true distance matrices (shortest-path or average by O-D), cost or toll matrices, and subarea O-D matrix traversals using the Standard and Parallel Standard Traffic Assignments. And the Emme Path-based Traffic Assignment saves paths so that you can analyze them without re-running the assignment.

Transit Assignments. From planning to operations, Emme offers a range of transit assignments to suit your needs. Evaluate the transport policies that are relevant to you, including frequencies, timetables, vehicle capacity, crowding, fare schemes, and more.

• Standard Transit Assignment. Sophisticated multimodal, multipath transit assignment that minimizes the expected travel cost.
• Timetable Assignment. Complete timetable assignment which uses detailed departure and arrival information to derive an optimal path.
• Disaggregate Transit Assignment. Permits the detailed analysis of individual transit trips, where the origins and destinations are specified as precise coordinates or node numbers rather than zone numbers.

The Emme Transit Assignment offers a sophisticated multipath assignment; a multipath or ‘strategy’ is a generalization of the concept of a path. In Emme, travellers may choose from elements that are more complex than a simple path toward a destination; for instance they may choose a set of paths, and let the vehicle that arrives first at a stop determine which of these paths to take.

The Emme Transit Assignment supports multiclass assignments on multimodal networks, and, as with Traffic Assignments, transit time functions are open and fully user-specified. Also typical of Emme procedures, the implementation of the Emme Transit Assignment makes it possible, sometimes trivial, to implement variations on the procedure including capacity restraint, incremental, or disaggregate transit assignments.

The Emme Transit Assignment also provides native capabilities for detailed, disaggregate transit analysis of individual trips, such as for disaggregate destination choice models or disaggregate mode choice models, as well as for timetable-based transit assignments, which are most relevant when there is rich itinerary data, for example in national or regional services or operational-level studies.

The Emme Transit Assignment allows for the implementation of various transit fares, and it is possible to model the influence of fare on the traveller’s route choice via a combination of boarding penalties, distance-based components, and penalties associated with fare zone boundaries.

The Emme Transit Assignment also provides sensitivity to transit-segment specific attributes, allowing the possibility to implement sophisticated iterative solutions to effectively address congestion in transit networks, whereby crowding on certain transit segments can decrease the comfort of passengers in the vehicle, whereby passengers are prevented from boarding transit vehicles where there is no more room, or where transit vehicles on long transit-lines may “bunch” on congested corridors.

Strategy Analysis. In the same way that Emme Path Analysis tools complement Emme Traffic Assignment tools, Emme Strategy Analysis capabilities complement the Transit Assignment tools to address a large class of transit planning questions related to analyzing transit strategies. After a transit assignment is executed, it is possible to use a comprehensive set of strategy analysis keywords and operators, which, when used in conjunction with each other, can drive applications like the computation of distance matrices, select-link or select-line analyses, station-to-station matrices, line-to-line transfers, or to compute fare matrices corresponding to a desired fare structure.

The Emme Matrix Calculators and Matrix Balancing procedures provide a comprehensive framework with which to implement virtually any zonal-level travel demand forecasting model, from the classical 4-step model to multimodal assignment with direct demand functions, as well as aggregate demand models based on trip chains.

Matrix Calculators. The Emme Matrix Calculators provide a general and productive way to work with demand modelling data like socioeconomic demographics or zonal data, alongside any other input, output, or intermediate matrix data involved in a transport model. Instead of fixed demand modelling procedures, Emme provides a comprehensive and flexible set of tools for matrix manipulations.

Matrix Calculations are also instrumental to achieve a variety of general purpose tasks, including computation of intrazonal impedances, incorporation of parking costs, market segmentation of demand, or, in conjunction with the Emme Traffic and Transit Assignment tools, to accomplish an array of matrix adjustment procedures and survey-location optimizations. Matrix calculations also play an important role in preparing travel demand management models (carpooling/vanpooling, telecommuting, etc.), and peak spreading models. And, the Matrix Calculators are also easily used for implementing evaluation methods based on demand and service levels.

The Emme Matrix Calculators also perform generalized matrix-product operations involving intermediate zones; this provides a foundation with which to implement a variety of trip chaining models including park-and-ride/kiss-and-ride models, or aggregate activity-based travel demand models.

Matrix Balancing Procedures. Two- and three-dimensional Emme Matrix Balancing procedures provide the building blocks for implementing various spatial interactions or trip distribution models; because Emme provides these underlying tools in addition to integrated procedures, users are free to customize or create local variations on the theme.

Two-dimensional matrix balancing procedures give modellers the ability to implement a variety of aggregate trip distribution models natively in Emme. For example, when used in conjunction with the Emme Matrix Calculators to prepare matrix inputs, implementations of Fratar, entropy, or gravity trip-distribution models are straightforward. And whatever the methodology used for calibration, modellers are free to automate other Emme tools, such as using matrix calculations to balance productions and attractions or assignments to provide feedback effects.

Emme’s three-dimensional matrix balancing procedures can be used to further refine versions of distribution models by including an additional constraint, allowing even more sophisticated applications in which demand can reproduce, for instance, a given travel time distribution, a set of screen line counts, etc… in addition to production and attraction constraints.

Network Calculators. The Emme Network Calculators provide a powerful and general means of carrying out specialized analyses without the need for custom scripting or external programming, including basic statistical summaries of network data, a wide-variety of results post-processing for performance analysis and evaluation, even iterative network modifications required in the implementation of more sophisticated multi-stage modeling features.

The Emme Network Calculators provide comprehensive access to network data in the Emme Database and open expression of user-defined algebraic expressions. The Emme Network Calculators also provide seamless in-place aggregations between network data so there’s no need for SQL-programming or join-style operations. Emme Network Calculators play an important role in a variety of modeling tasks, including validation and calibration of network data, user-defined statistics and summaries (volume/capacity ratios, vehicles on subnetworks, etc…), evaluation and impact analyses (emissions, cold-starts, etc…), in combination with Emme Matrix Calculators (VHT,VKT/VMT, etc…) and in many other automated procedures.

Automation Framework. Emme provides a powerful macro language for the automation of repetitive and frequently used commands. The macro language provides programming facilities such as conditional branching, parameter substitution, calls to other macros and third-party utilities. It also includes a single-step debugging mode. The macro language makes it possible to implement complex sequences of computations or even algorithms which use the tools described here as building blocks.

Together with the general purpose Emme transport planning tools summarized here, Emme offers planners and modellers a real toolkit for implementing a wide variety of models, and for re-using or customizing established procedures created by INRO, or by other Emme users.