Skim Outputs ¶

Travel Model Two generates comprehensive level-of-service (LOS) matrices called “skims” that represent impedances and costs between zones for different transportation modes and time periods.

Highway Skims ¶

Highway Skim Matrices (OMX Format) ¶

File Pattern: skim_matrices/highway/HWYSKM[TimePeriod]_taz.omx

Contains multiple matrices with highway travel impedances between Traffic Analysis Zones (TAZs):

Travel Time - Peak and off-peak periods
Distance - Network distance in miles
Bridge Tolls - Toll costs for bridge crossings
Operating Costs - Vehicle operating costs
Generalized Cost - Combined time and cost impedance

Vehicle Types Included:

Vehicle	Description
`DA`	Drive Alone
`S2`	Shared 2-person
`S3`	Shared 3+ person
`DATOLL`	Drive Alone with toll facilities
`S2TOLL`	Shared 2-person with toll facilities
`S3TOLL`	Shared 3+ person with toll facilities
`TRK`	Truck
`TRKTOLL`	Truck with toll facilities
`LRGTRK`	Large Truck
`LRGTRKTOLL`	Large Truck with toll facilities

Skim Components:

Component	Description
`time`	pure travel time in minutes
`dist`	distance in miles
`cost`	cost
`hovdist`	distance on HOV facilities
`tolldist`	distance on toll facilities
`freeflowtime`	free flow travel time in minutes
`bridgetoll_{vehicle}`	bridge tolls, {vehicle} refers to toll group
`valuetoll_{vehicle}`	other, non-bridge tolls, {vehicle} refers to toll group
`rlbty`	Reliability
`autotime`	Auto Time

MAZ-to-MAZ Highway Skims ¶

File Pattern: skim_matrices/highway/HWYSKIM_MAZ_MAZ_DA.csv

Format: CSV with columns:

FROM_ZONE, TO_ZONE, COST, DISTANCE, BRIDGETOLL

Content: - Shortest path costs between Micro Analysis Zones (MAZs) - Distance in miles - Bridge toll costs - Generalized cost (time + operating cost + tolls)

Drive Access Skims ¶

File Path: skims/drive_access_skims.csv

Format: CSV with columns:

FTAZ,MODE,PERIOD,TTAP,TMAZ,TTAZ,DTIME,DDIST,DTOLL,WDIST

Content: - Drive access times and costs to transit stops - Walking distances from parking to transit access points - Used for park-and-ride and kiss-and-ride mode choice

Transit Skims ¶

Transit Skim Matrices (OMX Format) ¶

File Pattern: skims/trnskm[TimePeriod]_[TransitClass].omx

Transit Classes:

Transit Class	Description
`WLK_TRN_WALK`	Walk to and from transit
`PNR_TRN_WLK`	Drive to transit (Park and Ride) and Walk from transit
`WLK_TRN_PNR`	Walk to transit and Drive from transit
`KNR_TRN_WLK`	Kiss N Ride to Transit (Drop Off) and walk from transit
`WLK_TRN_KNR`	Walk from transit and kiss n ride from transit (Pick Up)

Skim Components:

Components	Description
`IWAIT`	Initial wait time
`XWAIT`	Transfer wait time
`WAIT`	Total wait time
`FARE`	Transit fare cost
`BOARDS`	Number of boardings
`WAUX`	Walk auxiliary time
`DTIME`	Drive access time
`DDIST`	Drive access distance
`IVT`	Total in-vehicle time
`IN_VEHICLE_COST`	In-vehicle cost
`WACC`	Walk access time
`WEGR`	Walk egress time
`CROWD`	Crowding penalty (if enabled)
`XBOATIME`	Transfer Boarding Time Penalty
`DTOLL`	Drive access/egress toll price
`TRIM`	Used to Trim demand

Mode-Specific In-Vehicle Times:

Mode	Description
`IVTCOM`	Commuter rail in-vehicle time
`IVTEXP`	Express bus in-vehicle time
`IVTFRY`	Ferry in-vehicle time
`IVTHVY`	Heavy rail in-vehicle time
`IVTLOC`	Local bus in-vehicle timee
`IVTLTR`	Light rail in-vehicle time

Congested Transit Skims (Optional) ¶

When congested transit assignment is enabled, additional skim components:

LINKREL - Link reliability
EAWT - Extra added wait time
CAPPEN - Capacity penalty

Active Mode Skims ¶

Pedestrian Distance Skims ¶

Files:

skims/ped_distance_maz_maz.txt - MAZ to MAZ walking distances

Bicycle Distance Skims ¶

Files:

skims/bike_distance_maz_maz.txt - MAZ to MAZ cycling distances
skims/bike_distance_taz_taz.txt - TAZ to TAZ cycling distances

Format: CSV with columns:

from_zone,to_zone,dist

Time Periods ¶

All skim matrices are generated for these time periods:

EA - Early AM (3:00-6:00)
AM - AM Peak (6:00-10:00)
MD - Midday (10:00-15:00)
PM - PM Peak (15:00-19:00)
EV - Evening (19:00-3:00)

Usage Notes ¶

OMX Files: Use the OpenMatrix Python library or Emme to read OMX format files
Matrix Names: Follow the pattern [TimePeriod]_[VehicleType]_[SkimComponent]
Zone Systems: TAZ-based for regional analysis, MAZ-based for local access analysis
Units: Time in minutes, distance in miles, costs in dollars (2000$)
Missing Values: Large values (>1e19) indicate no connection between zones