Bike Model

Slope, adjacent traffic volume and bicycle provisions are three factors used to estimate perceived travel cost for bike mode.

For additional information on the Bike Model see the SoundCast Wiki: https://github.com/psrc/soundcast/wiki/Bike-Model

Slope Calculation

The slope used in the model is named cumulative slopes. It refers to the total elevation change experienced along a bike facility, calculated by summing the elevation differences at 30-foot interval along the bike facility. This measure captures the overall uphill and downhill effort required for a cyclist to traverse a particular segment of the network.

The calculation uses USGS DEM 30-foot raster file. It is now integrated into BKRCast. Turn on the calculation by setting run_cumulative_slopes = True. Or run the following command.
python scripts/bikes/calculate_cumulative_slopes_for_bike.py

The following steps are taken to calculate cumulative elevation gains.
Step 1: convert EMME network (links) to shape file
Step 2: split the link shape file into points with 30-foot interval.
Step 3: overlay the points on the elevation raster (from USGS DEM with resolution 30-foot).
Step 4: calculate elevation at each point using rasterstats.point_query(). Use multi-processing technique to speed up the processing.
Step 5: calculate cumulative elevation gains on each bike facility, and cumulative slope as well.

Click here to find more info regarding the slope calculation.

Network Coding

Bike facility in EMME network is flagged in @biketype attribute.

@biketype

Value	Description
1	Separated bike lane
10	Bike trail
2	Bike lane striped
3	Bike shoulder (Kirkland does not have this category)
4	Wider lane/shared shoulder (Redmond does not have this category)

City of Bellevue uses more bike facility categories in bike lane planning. The lookup table is given below.

COB Bike Facility Code	Description	@biketype
O	Offstreet path - Bidirectional on one side of the street (e.g. NE 12th St) or independent of street network (e.g. ERC Trail), or one-way on both sides of the street (i.e., Spring Blvd raised bikeway)	10
AA	Two-way protected bikeway (on-street)	1
A	Protected bikeway (on-street bike lane with vertical separation, e.g. posts and planter boxes)	1
B	Bike lanes – striped (paint line) or buffered (painted horizontal separation only)	2
C	Bike shoulder	3
D	Shared shoulder (paved)	4
E	Wide outside lane	4
F	Shared wide outside lane	4
G	Sharrows (i.e., shared lane markings)	4

@biketype is used to calculate facility weight which is given below.

Bike Weights

Three important attributes(bike weights) are used in the calculation of bike cost: volume weight, facility weight, and slope weight.

1. volume_wt

AADT Range	volume_wt
<10k	0
10k - 20k	0.368
20k - 30k	1.40
>30k	7.157

2. facility_wt
   Different facility weights are assigned to bike lanes or trails, categorized by @biketype. So far the bike model has ability to differentiate three types of facilities, named premium (Trail/Separated bike lane), standard (bike lane striped, Bike shoulder, and Wider lane/shared shoulder), or none. The facility types are saved in @bkfac. Be aware that this attribute is only used in DaySim, not in EMME databanks.

@biketype	@bkfac	facility_wt
0	none	0
1, 10	premium	-0.860
2, 3, 4	standard	-0.108

3. slope_wt
   Slopes are grouped to three categories and different weights are assigned.

@upslp range	slope_wt
<2%	0.0
2% - 4%	0.371
4% - 6%	1.203
>6%	3.239

Total weight is calculated by adding one and inverse of premium bike weight to facility weight or the sum of the three weights.
For premium facilities, total weight is calculated by:
total_wt = 1 - premium_bike_weight + facility_wt
For other facilities, total weight is calculated by:
total_wt = 1 - premium_bike_weight + facility_wt + slope_wt + volume_wt

Total weight is used to model people's perception when comparing bike facilities, relative to a base of a separated bike trail (premium facility) with no slope. Weight calculation results are exported to bike_attr.csv for off model analysis. The total weight is exported to an EMME attribute file named bkwt.in.

Assignment and Skimming

Bike volume are assigned to bike network through EMME's extended transit assignment tool.

Note that in Emme, non-motorized trips are assigned using transit assignment, and are considered “auxiliary modes.” Traditionally these modes were only used to access transit, but in this case since we only provide bike demand and no transit options, the assignment occurs only for bikes.

matrix name	Description	Data Source
mf'bike'	bike demand	Daysim output
mf'recbike'	recreational bike demand	outputs from rec bike model (supplemental)
mf'bkpt'	perceived travel time	bike model output (from assignment)
mf'bkat'	actual travel time	bike model output (from skimming)

The assigned regular bike volume is saved in @bvol, and recreational bike volume in @recbvol.
Bike mode is not available between 8PM and 7AM.

Input Files

The input files are saved in [base_inputs]\bikes folder.

Name	Description
bike_counts.csv	Bike counts in roadway network
emme_attr.in	Bike attributes in roadway network
bkwt.in	Total bike weight for roadway links. Exported by the bike model script.

Output Files

Name	Path	Description
bike_volumes.csv	outputs\	bike model volumes
bike_attr.csv	outputs\	bike weight outputs