February 10, 2004
SUBJECT: Comparison of Vehicle Trip Forecasts for Big Box
Stores
At your request, I have prepared a series of comparisons of
the amount of weekly traffic typically generated by discount superstores (e.g.
Super Wal-Mart), discount clubs (e.g. Costco), and home improvement superstores
(e.g. Home Depot). The traffic volume estimates in this letter are based on
studies compiled by the Institute of Transportation Engineers (ITE) in Trip
Generation, 7th Edition. This publication is the definitive
source for estimating trips generated from different land use types. This
edition was recently updated in late 2003 to include recent traffic studies conducted
over the last six years. The information provided in this letter includes total
daily trips by the day of the week and total weekly trips.
ITEs complete descriptions of these three land uses
together with the various traffic data plots from Trip Generation, 7th
Edition are enclosed for your information. My summaries and examples of these
definitions are as follows:
v Discount
Superstore (ITE Land Use Code 813) free standing discount stores offering
a variety of customer services with a wide range of products that also contain a
full service grocery department under the same roof; (e.g. Super Wal-Mart)
v Discount
Club (ITE Land Use Code 861) discount store or warehouse where shoppers
pay a membership fee with discounted prices on items such as food, clothing,
tires, and appliances; (e.g. Costco)
v Home
Improvement Superstore (ITE Land Use
Code 862) free standing facilities that specialize in the sale of home
improvement merchandise such as lumber, tools, paint, lighting, wallpaper and
paneling, kitchen and bathroom fixtures, lawn equipment and plant and garden
accessories; (e.g. Home Depot)
Table 1 below provides the trip rates
per 1,000 square feet for a free standing discount superstore with an assumed
store size of 200,000 square feet using the data provided in Trip
Generation, 7th Edition. The fitted curve equations have been used
for weekdays and Saturdays as the points in the data plot near the store size
of 200,000 square feet are closer to the fitted curve line than they are to the
weighted average line. In fact as shown in the data plots, nearly all of the
data points are above the fitted curve line for stores in the upper end of the
data range, indicating even these fitted curves may understate the number of
trips for the larger stores. In addition, the following table also provides
both the low and the high ends of the range of trip rates for weekdays,
Saturdays, and Sundays.
Table
1
Trip Rates from Land Use 813 (Free
Standing Discount Superstore)
For An Assumed Store Size of 200,000
Square Feet
|
|
Number
of Studies |
Average Trip
Rate |
Low End
of Range of Rates |
High End
of Range of Rates |
|
|
|
|
|
|
|
Weekday Rate |
10 |
74.12(X)
3,977* |
29.65 |
64.03 |
|
Saturday Rate |
10 |
84.74(X)
- 4,347* |
35.32 |
73.61 |
|
Sunday Rate |
10 |
46.98 |
27.61 |
70.21 |
|
|
|
|
|
|
Source: Institute of
Traffic Engineers, Trip Generation, 7th Edition.
* indicates fitted curve
equation was used instead of average trip rate
X indicates store size in
1,000 square feet
Table
2 below provides a comparison of trips associated with a discount superstore of
200,000 square feet for weekdays, Saturdays, and Sundays using the average trip
rates described above as well as for the low and high ends of the range of trip
rates published by ITE in Trip Generation, 7th Edition.
Table
2
Daily/Weekly Trips from Land Use 813
(Free Standing Discount Superstore)
For An Assumed Store Size of 200,000
Square Feet
|
|
Number
of Studies |
Average Trip
Rate |
Low End
of Range of Rates |
High End
of Range of Rates |
|
|
|
|
|
|
|
Weekday Trips |
10 |
10,847* |
5,930 |
12,806 |
|
Saturday Trips |
10 |
12,601* |
7,064 |
14,722 |
|
Sunday Trips |
10 |
9,396 |
5,522 |
14,054 |
|
Weekly Trips |
|
76,232 |
42,236 |
92,806 |
Source: Institute of
Traffic Engineers, Trip Generation, 7th Edition.
* indicates fitted curve
equation was used instead of average trip rate
Table 3 below provides the trip rates
per 1,000 square feet for a discount club with an assumed store size of 136,000
square feet. Trip rates for weekdays, Saturdays, and Sundays are shown using
the data provided in Trip Generation, 7th Edition. The weighted
average trip rates have been used in all three cases as fitted curve equations
have not been developed by ITE for this land use. In addition, the following
table also provides both the low and the high ends of the range of trip rates
for weekdays, Saturdays, and Sundays.
Table
3
Trip Rates from Land Use 861 (Discount
Club)
For An Assumed Store Size of 136,000
Square Feet
|
|
Number
of Studies |
Average Trip
Rate |
Low End
of Range of Rates |
High End
of Range of Rates |
|
|
|
|
|
|
|
Weekday Rate |
19 |
41.80* |
25.44 |
78.02 |
|
Saturday Rate |
16 |
53.75* |
31.96 |
82.43 |
|
Sunday Rate |
8 |
33.67* |
17.17 |
61.79 |
|
|
|
|
|
|
Source: Institute of
Traffic Engineers, Trip Generation, 7th Edition.
* indicates average rate was
used as fitted curve equation was not given
Table
4 below provides a comparison of trips associated with a discount club of
136,000 square feet for weekdays, Saturdays, and Sundays using the average trip
rates described above as well as for the low and high ends of the range of trip
rates published by ITE in Trip Generation, 7th Edition.
Table
4
Daily/Weekly Trips from Land Use 861
(Discount Club)
For An Assumed Store Size of 136,000
Square Feet
|
|
Number
of Studies |
Average Trip
Rate |
Low End of
Range of Rates |
High End
of Range of Rates |
|
|
|
|
|
|
|
Weekday Trips |
19 |
5,685* |
3,460 |
10,611 |
|
Saturday Trips |
16 |
7,310* |
4,347 |
11,210 |
|
Sunday Trips |
8 |
4,579* |
2,335 |
8,403 |
|
Weekly Trips |
|
40,314 |
23,982 |
72,668 |
Source: Institute of
Traffic Engineers, Trip Generation, 7th Edition.
* indicates average rate was
used as fitted curve equation was not given
Table 5 below provides the trip rates per
1,000 square feet for a home improvement superstore with an assumed store size
of 108,000 square feet. Average trip rates for weekdays, Saturdays, and Sundays
are shown using the data provided in Trip Generation, 7th Edition.
The fitted curve equation has been used for weekdays as the points in the data
plot near the assumed store size of 108,000 square feet are closer to the
fitted curve line than they are to the weighted average line. In addition, the
following table also provides both the low and the high ends of the range of
trip rates for weekdays and Saturdays.
Table
5
Trip Rates from Land Use 862 (Home
Improvement Superstore)
For An Assumed Store Size of 108,000
Square Feet
|
|
Number
of Studies |
Average Trip
Rate |
Low End
of Range of Rates |
High End
of Range of Rates |
|
|
|
|
|
|
|
Weekday Rate |
9 |
Ln(T) =
0.70(Ln(X) + 4.85* |
18.35 |
39.31 |
|
Saturday Rate |
2 |
45.67 |
34.77 |
49.99 |
|
Sunday Rate |
1 |
20.93 |
Not
given |
Not
given |
|
|
|
|
|
|
Source: Institute of
Traffic Engineers, Trip Generation, 7th Edition.
* indicates fitted curve
equation was used instead of average trip rate
Ln indicates logarithmic
relationship where T is number of trips and X is store size in 1,000 square
feet
Table
6 below provides a comparison of trips associated with a home improvement
superstore of 108,000 square feet for weekdays and Saturdays using the average
trip rates described above as well as for the low and high ends of the range of
trip rates published by ITE in Trip Generation, 7th Edition.
Table
6
Daily/Weekly Trips from Land Use 862
(Home Improvement Superstore)
For An Assumed Store Size of 108,000
Square Feet
|
|
Number
of Studies |
Average Trip
Rate |
Low End
of Range of Rates |
High End
of Range of Rates |
|
|
|
|
|
|
|
Weekday Trips |
9 |
3,386* |
1,982 |
4,245 |
|
Saturday Trips |
2 |
4,932 |
3,755 |
5,399 |
|
Sunday Trips |
1 |
2,260 |
Not
given |
Not
given |
|
Weekly Trips |
|
24,122 |
|
|
Source: Institute of
Traffic Engineers, Trip Generation, 7th Edition.
* indicates fitted curve
equation was used instead of average trip rate
In comparing the tables above for
discount superstores and discount clubs, and using the average trip rates for
the assumed store sizes, a discount superstore would be expected to generate
over 76,000 trips during a week, nearly double the 40,000 trips generated by a
discount club. Using the low end of the range of rates, a discount superstore
would be expected to generate over 42,000 trips during a week, more than 75
percent higher than the 24,000 trips generated by a discount club at the low
end of the range of rates. Using the high end of the range of rates, a discount
superstore would be expected to generate nearly 93,000 trips during a week,
over 25 percent higher than the 73,000 trips generated by a discount club at
the high end of the range of rates.
In comparing the tables above for
discount superstores and home improvement superstores, and using the average trip
rates for the assumed store sizes, a discount superstore would be expected to
generate over 76,000 trips during a week, more than triple the 24,000 trips
generated by a home improvement superstore.
Respectfully
submitted,
Tom Brohard and Associates
Tom
Brohard, PE
Principal