Available with Network Analyst license.
Travel modes on a network dataset define how a pedestrian, car, truck or other medium of transportation moves through the network. A travel mode can be general—for example, to model typical trucks—or more specific, such as to model ladder trucks or rescue trucks.
Override values are the key elements that make a travel mode. By preconfiguring a travel mode on a network dataset, you provide several override parameter values. Together, the parameters describe a travel mode, or the actions that are allowed on the network and how the actions can be performed. When you perform an analysis, a travel-mode parameter lets you choose your predefined travel mode and, in essence, it automatically sets the values for related analysis properties that also define travel modes. (In reality, the parameter values are overridden rather than automatically set.) The benefits are time savings and reduced complexity—you don't need to remember and configure, with each analysis, the parameter values that most accurately characterize the vehicles you are modeling.
Example: Ladder and rescue trucks
A fire department frequently performs route analyses to find the quickest way for their vehicles to reach an incident. The vehicles vary in size and maneuverability. To compare ladder and rescue trucks, for instance, rescue trucks are faster than ladder trucks, so their travel times are shorter; ladder trucks are taller and face more height restrictions, which can result in longer routes; and unlike rescue trucks, ladder trucks cannot make U-turns at intersections, which can exclude time-saving opportunities.
Whenever dispatchers solve a route analysis for a ladder or rescue truck without using travel modes, they need to set various analysis properties to appropriately model the truck they are routing. They do this by choosing an impedance value to model the travel time, setting values for height restrictions and U-turn policies, and defining several other vehicle-specific properties.
Setting these parameters at the time of analysis is avoided, however, by using travel modes. The fire department creates two travel modes on the network dataset: Ladder Truck and Rescue Truck. Each is assigned override values for the vehicle-specific travel parameters. When dispatchers need to generate a route for a ladder truck, they set a travel-mode parameter on the analysis to Ladder Truck and skip the process of explicitly setting properties for the vehicle's impedance, vehicle height, U-turn policy, and so on. Instead of setting several parameters with each route analysis, they set one.
Override parameters
This section lists the override parameters you define when adding a travel mode to a network dataset. It also provides examples of how override values may differ between travel modes.
Impedance—Specifies the cost attribute on which to optimize the analysis.
A travel mode modeling cars would need a cost attribute that stores the time it takes a car to traverse an edge or street segment. In contrast, a Walking Time travel mode would need a cost attribute storing the time it takes to walk along edges or streets. A distance-based cost attribute, such as Meters, can be chosen for either a Driving Distance or Walking Distance travel mode.
Time Attribute—Specifies the time-based cost attribute for reporting directions.
The choices for Impedance and Time Attribute are typically the same when modeling time-based travel modes. When modeling distance-based travel modes, however, the Time Attribute value would need to describe how long it takes the travel mode to travel along network edges. For a Walking Distance travel mode, for instance, Time Attribute would be set to a cost attribute storing walking times.
Distance Attribute—Specifies the distance-based cost attribute for reporting directions and for solving vehicle routing problems.
Driving Time and Waking Time travel modes would need Distance Attribute set to a distance-based cost attribute, such as Meters.
U-Turns at Junctions—Indicates where the travel mode is allowed to make U-turns.
A travel mode that models trucking time would likely have U-Turns at Junctions set to Not Allowed. Yet, Walking Distance would have it set to Allowed, since pedestrians can easily turn around anywhere.
Simplification Tolerance—Specifies whether the travel mode generalizes the geometry of analysis results and by how much.
Larger simplification values result in reduced bandwidth requirements and rendering times, but the output line and polygon features aren't as clear, especially as you zoom in on the map. Output routes for walking modes are not simplified as much as they are for driving modes. Pedestrian routes are viewed at larger map scales, so more detail is needed for the route lines.
Use Hierarchy—Indicates whether the travel mode uses the network hierarchy in an analysis.
Driving travel modes use hierarchy, but walking modes don't; drivers tend to be more willing to travel farther to avoid complicated routes that have more turns and stops. Pedestrians tend to prefer shorter distances, even if the route is more complex.
Restrictions—Indicates the restriction attributes that are respected during solve time.
A Trucking Time - Corrosive travel mode may set several restrictions to require trucks to follow designated truck routes when possible, avoid roads where corrosive-materials cargo is prohibited, and so on. Walking modes often have restrictions set that prohibit highways where pedestrians are not allowed. Furthermore, wheelchair travel modes restrict stairs.
Parameter Values—Specifies the parameter values for network attributes that have parameters.
A Trucking Time travel mode can set a Vehicle Height parameter to prevent the vehicle from going under bridges where that type of truck won't fit. For walking-time travel modes, walking speed is often set as parameter.
Create travel modes
Travel modes are added to a network dataset. You can create travel modes through ArcMap's Catalog window.
Use travel modes
The ArcGIS Network Analyst extension is available in various ArcGIS products. Yet, performing network analysis with travel modes is slightly less accessible. The following list describes where travel modes can and cannot be used when performing a network analysis:
Travel modes are not exposed in network analysis layers in ArcMap, so you won't see a travel-mode property in the Layer Propertiesdialog box.
You can expose travel modes on your Network Analysis services using ArcGIS for Server. In ArcMap, create a network dataset that includes travel modes, create a network analysis layer on the network dataset, and publish the map document as a service. Although a travel-mode property isn't exposed on the network analysis layer in ArcMap, travel modes are detected on the network dataset. Once published, a travelMode parameter is available on the endpoint of the Network Analysis service.
The geoprocessing tools for performing analyses in System Toolboxes > Network Analyst Tools > Server include a Travel Modeparameter. You can perform network analyses in ArcMap using these tools. Furthermore, if you publish the results of one of these tools as a geoprocessing service, the Travel Mode parameter is available in the service.
The following geoprocessing tools create network analysis layers: Make Closest Facility Layer, Make Location-Allocation Layer, Make OD Cost Matrix Layer, Make Route Layer, Make Service Area Layer, and Make Vehicle Routing Problem Layer. They don't expose travel modes, but the network analysis layers you create can be modified to use a travel mode through the Network Analyst Python Module.