Appendix D Traffic Impact Analysis - westplainseis.com

5.5 Trip Types
Retail and multi-use developments experience a number of different trips types, Shared (or Internal)
Trips, Pass-by trips and New trips. These trip types are further described below.
Shared (Internal) Trips - These are trips which occur on or within the site where a vehicle will
stop at more than one place on the site or a patron will visit multiple uses on a site. For example,
someone destined for big-box store may also visit a restaurant on the site. For Alternatives 1 and
2, the Casino was treated as a retail use and the 20% retail to retail reduction rate was used.
Standard ITE Retail to Office shared trip rates were utilized for trips between the office and both
the Shopping Center and Casino components. For Alternative 1, potential trips associated with
the hotel component are captured and included within the trip rate applied to the casino
component as is the case with the source document and data used as the basis for the casino trip
rate used for this study.
Pass-by Trips - These trips represent vehicles which currently use adjacent roadways providing
primary access to the new land use / project. These trips, however, have an ultimate destination
other than the project in question. They should be viewed as drop-in customers who stop in on
their way to/from work or on their way to/from another site. Pass-by trips add turning
movements to the site access points but do not represent additional trips to the greater
transportation system.
For this particular project, pass-by traffic would come primarily from the existing traffic stream
on Highway 2 with a lesser amount coming from Craig Rd.
Based on information in the ITE Trip Generation Handbook, the pass-by rate for a “Shopping
Center” for PM peak hour is 34%; the pass-by rate for “Quality Sit-down Restaurant” is 44%.
No published pass-by trip rates are available for the casino/hotel use. For the purposes of this
analysis a conservative 5% pass-by rate was assumed for the casino use in Alternative 1.
New (External) Trips - These trips occur only to access a specific land use such as the discount
superstore. These types of trips will travel to and from the new site and a single other destination
such as home. This is the only trip type that will result in a net increase in the total amount of
traffic within the study area.
For this project shared trips were calculated based on ITE procedures documented in the Trip Generation
Handbook. Refer to the appendix for detailed calculations of shared trips for each alternative and phase
of development. The resulting shared trip percentages reduction for each alternative at buildout is as
follows: Alternative 1- 19.6%; Alternative 2- 19.0%; Alternative 3- 13.4%.
Pass-by trips were initially calculated passed on the rates discussed above. Per common industry practice
all pass-by trips should not exceed 10% of the adjacent street(s) traffic volume; for this project the cap
guideline applied for each alternative and phase and adjustments were made accordingly. The resulting
effective pass-by rate for each alternative is as follows: Alternative 1- 11.7%; Alternative 2- 11.5%;
Alternative 3- 16.3%.
West Plains Development – Spokane Tribe Page | 47
Traffic Impact Analysis April 28, 2011