Introduction
I would like to share the results of a few speed limit studies recently done in Topeka. Two major arterials were studied, Fairlawn and Huntoon. The traffic studies concluded that these two arterials should be changed from 35 mph to 40 mph. The results were as expected. The 85 th percentile speeds went up about one mph; there was not much of a change in the average, the pace, or percent in pace. The big change as expected was the percent over posted dropped substantially. Charts are below for these two roadways as well as two other streets.
Fairlawn Road
Fairlawn Road is a major arterial that is mainly five-lane section; this segment of roadway is approximately four miles in length. The before speed limit was 35 mph and the after was 40 mph.
Location |
Before 85 th |
After 85th |
Before Average |
After Average |
Before Pace |
After Pace |
Before % in Pace |
After % in Pace |
Before % over posted |
After % over posted |
Summerfield |
40 |
41 |
36 |
36 |
32-41 |
32-41 |
79 |
77 |
56 |
16 |
33 rd Terrace |
40 |
42 |
37 |
37 |
33-42 |
34-43 |
82 |
81 |
69 |
21 |
31 st Terrace |
40 |
42 |
37 |
38 |
32-41 |
34-43 |
86 |
80 |
66 |
25 |
27 th Terrace |
40 |
40 |
36 |
37 |
32-41 |
32-41 |
90 |
88 |
68 |
7 |
23 rd Street |
39 |
40 |
36 |
37 |
31-40 |
32-41 |
88 |
88 |
53 |
7 |
19 th Terrace |
38 |
38 |
35 |
34 |
30-39 |
29-38 |
83 |
91 |
51 |
3 |
15 th Street |
39 |
40 |
35 |
36 |
31-40 |
31-40 |
82 |
88 |
43 |
9 |
12 th Street |
41 |
40 |
37 |
37 |
32-41 |
33-42 |
79 |
86 |
64 |
10 |
9 th Street |
39 |
39 |
36 |
36 |
31-40 |
31-40 |
88 |
87 |
51 |
4 |
N. of 8 th Ave |
39 |
39 |
35 |
35 |
30-39 |
30-39 |
83 |
82 |
43 |
4 |
Huntoon Street
Huntoon Street is a five-lane major arterial; this section of roadway is approximately two miles in length. The before speed limit was 35 mph and the after was 40 mph.
Location |
Before 85 th |
After 85th |
Before Average |
After Average |
Before Pace |
After Pace |
Before % in Pace |
After % in Pace |
Before % over posted |
After % over posted |
Harvey |
42 |
43 |
38 |
39 |
33-42 |
35-44 |
83 |
84 |
77 |
30 |
W. of Belle |
40 |
42 |
37 |
38 |
32-41 |
33-42 |
92 |
79 |
64 |
25 |
Luther East Dr |
41 |
41 |
37 |
38 |
31-40 |
33-42 |
77 |
82 |
60 |
22 |
Burnett |
41 |
42 |
37 |
39 |
33-42 |
34-43 |
86 |
83 |
64 |
31 |
57 th Street is about one mile in length.
Location |
Posted |
85 th |
Mean |
Pace |
% in Pace |
% Over Posted |
Westbound Before |
25 |
35 |
29 |
25-34 |
69 |
79 |
Westbound After |
35 |
37 |
32 |
29-38 |
75 |
25 |
|
|
|
|
|
|
|
Eastbound Before |
25 |
38 |
32 |
27-36 |
62 |
86 |
Eastbound After |
35 |
39 |
34 |
29-38 |
73 |
37 |
Chatham Street is a one-mile collector running between two major arterials that was changed from 30 mph to 35 mph.
Speed Limit |
85 th Percentile |
50 th Percentile |
Average Speed |
10 mph Pace |
Percent in Pace |
% Over Posted |
30 mph |
39 mph |
34 mph |
34 mph |
29 – 38 |
69.1 |
74.2 |
35 mph |
39 mph |
34 mph |
35 mph |
29 - 38 |
71.0 |
37.7 |
The results are what a traffic engineer would expect. We say that drivers drive at speeds that they feel comfortable with and not by the sign – I continue to believe this. There was little change in the numbers except for the percent of drivers in compliance with the law. On Fairlawn the average percent over posted reduced from 56 to eleven. Similarly on Huntoon, the percent in violations dropped from 66 to 27 percent.
Author
 Linda Voss, P.E.
Linda Voss is the City Traffic Engineer for Topeka, Kanasas. She was the MOVITE president in 2006 and now serves in the MOVITE board as the Immediate Past President.
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