TE 24a-1 (10/79)
File:
Troop:
New York State Department of Transportation
Traffic and Safety Division
LINEAR SPEED ZONE EVALUATION
HIGHWAY DEVELOPMENT INDEX & GEOMETRIC FACTOR
DETERMINATION SHEET
1. This form provides a means for determining whether a particular speed zone is or is not warranted.
The methodology used, independently examines both highway development and highway geometric
values. By comparing these values with statistically obtained state standards, a determination is made.
2. This form should be prepared to cover the portion of highway on which recommendations are based.
3. Separate Forms TE 24 should be prepared where a graduated zone is involved, since the different
speed limits should be justified for the sections of highway to which they apply.
4. This form, along with the LINEAR SPEED ZONE EVALUATION SHEET (Form TE 23) and the
SPEED DATA AND ANALYSIS SHEET (Form TE 27), should be used in all speed zone cases in-
volving consideration of a linear type regulation.
TE 24a-2 (10/79)
FORM INSTRUCTIONS
1. In Part A, compute the Highway Development Index.
2. In Part B, compute the Highway Geometric Factor.
3. If the Highway Development Index is > 50, a speed zone is warranted. The numerical value of that limit should be established at the 85^{th} percentile speed using the Speed Data Analysis Sheet (FORM TE 27) to compute it. If the 85^{th} percentile speed is determined to be 55 MPH or greater, the statewide 55 MPH speed limit prevails and a specific linear limit need not be established.
4. If the Highway Development Index is betweeen 0 and 50, enter the Criteria for Speed Zone Approval table under the Highway Development Index and find the range of values in which the computer Highway Development Index (Part A) is found. Compare the computed Highway Geometric Factor (Part B) to the corresponding Minimum Highway Geometric Factor in the table.
a. If the computed Highway Geometric Factor is greater than or equal to the table value, a speed zone not to exceed 55 MPH may be warranted. The numerical value of that limit should be established at the 85^{th} percentile speed using the Speed Data Analysis Sheet (FORM TE 27) to compute it. If the 85^{th} percentile speed is determined to be 55 MPH or greater, the statewide 55 MPH speed limit prevails and a specific linear limit need not be established.
2. If the computed Highway Geometric Factor is less than the table value, a speed zone is generally not warranted and should be denied. However, where conditions indicate that the prevailing speeds may be less than the statutory 55 MPH limit, a speed check may be conducted and used to establish a legal speed zone.
Criteria for Speed Zone Approval
Highway Development Index |
Minimum Highway Geometric Factor | |
< 3 Lanes |
> 3 Lanes | |
0 - 10 |
7.1 |
6.7 |
11 - 20 |
6.5 |
6.1 |
21 - 30 |
5.9 |
5.5 |
31 - 40 |
5.3 |
4.9 |
41 - 50 |
4.7 |
4.3 |
> 50 |
-- |
-- |
TE 24a-3 (10/79)
HIGHWAY DEVELOPMENT INDEX & GEOMETRIC FACTOR
DETERMINATION SHEET
_________________________________________________________________________________________________
Road Name & Route No. Jurisdiction & SH, CR or TH No. Length in Miles (nearest 10^{th})
_______________________________________________________________________________________________________________________________
Community Town County Date
_________________________________________________________________________________________________
Section Evaluated on this sheet - Identify with Respect to Data Sheet Line Diagram
1. HIGHWAY DEVELOPMENT INDEX
Left Right Left Right
Roadside Development:* Class I - Number of Units ______ ______ x 1.0 = ______ ______
Class II - Number of Units ______ ______ x 2.0 = ______ ______
Class III - Number of Units ______ ______ x 3.0 = ______ ______
Class IV - Number of Units ______ ______ x 4.0 = ______ ______
TOTAL ROADSIDE DEVELOPMENT ______ ______
Distribution of Roadside Development:
Distribution Factor = 0.5 + S / (S + s) = 0.5 + _________ = ______________
S = No. of Units on the Side of Highway Having the Greater
Roadside Development
s = No. of Units on the Side of Highway Having the Lesser
Roadside Development
________________________________________________________________________________________________
(Total Roadside Development x Distribution Factor) _________ x _________ = _________
Intersection Development:* Class A - Number ______ x 2.0 = _________
Class B - Number ______ x 3.0 = _________
Class C - Number ______ x 4.0 = _________
TOTAL HIGHWAY DEVELOPMENT _________
________________________________________________________________________________________________
HIGHWAY DEVELOPMENT INDEX = Total Highway Development
Length of Section in Miles _________
(nearest 10^{th})
* See over for detailed explanation
TE 24a-4 (10/79)
ROADSIDE DEVELOPMENT
Class I Residences, small commercial establishments, small public buildings and other units which generate light and/or occasional roadside activity.
Class II Average commercial establishments, district schools, trailer parks, light industries, public buildings, and other units generating roadside activity which would fit one or more of the following descriptions:
1. Continuous, but light
2. Moderate at certain regular times, as during commuting hours
3. Substantial on infrequent occasions
Class III Heavy industries, central schools, shopping centers and units generating continuous moderate roadside activity, or substantial activity at certain regular times.
Class IV Large shopping centers and other units generating substantial and continuous roadside activity. Some large industries which are tourist attractions or for some other reason generate substantial activity, in addition to heavy commuting traffic volumes, would be included in this category.
INTERSECTION DEVELOPMENT
Class A Intersecting road is of substantially less importance. Side road traffic and turning movements have little effect on the traffic flow pattern of the road under study.
Class B Intersecting road is of lesser importance, but side road traffic and turning movements are such that intersection has appreciable effect on the traffic flow pattern of the road under study.
Class C Signalized intersections, and intersections with roads of comparable or greater importance. Intersections which have a pronounced effect on the traffic flow pattern of the road under study.
TE 24a-5 (10/79)
2. HIGHWAY GEOMETRIC FACTOR
Pavement:
FACTOR | ||||
Predominant Travel-Lane Width (Feet) |
2 & 3 Lane Roadways |
Roadways of More Than 3 Lanes Undivided or Paved Flush Mall |
Unpaved or Raised Mall Narrower Than 10 Feet |
Unpaved or Raised Mall 10 Feet or Wider |
8 or Less |
1.6 |
1.4 |
1.0 |
0.9 |
9 |
1.4 |
1.2 |
0.9 |
0.8 |
10 |
1.2 |
1.0 |
0.8 |
0.7 |
11 |
1.1 |
0.9 |
0.7 |
0.6 |
12 or more |
1.0 |
0.8 |
0.6 |
0.5 |
PAVEMENT FACTOR ________________________
Roadway Characteristics:* |
o Excellent (1.0) |
o Good (1.2) |
o Average (1.4) |
o Adverse (1.6) |
o Poor (1.8) |
ROADWAY FACTOR ________________________
Shoulders:* |
o Good (0.9) |
o Average (1.1) |
o Poor (1.3) |
SHOULDER FACTOR ________________________
Sidewalks: |
o Inadequate or lacking where need exists (1.1) |
o Adequate or unnecessary (1.0) |
SIDEWALK FACTOR ________________________
Traffic:
AADT Volume ________________ |
Vehicles Per Lane Per Day |
Factor | |
No. of Travel Lanes ____________ |
5000 or more |
1.6 | |
3500 to 5000 |
1.4 | ||
2000 to 3500 |
1.2 | ||
1000 to 2000 |
1.0 | ||
Less than 1000 |
0.8 |
TRAFFIC FACTOR ________________________
HIGHWAY GEOMETRIC FACTOR (TOTAL) ________________________
* See over for detailed explanation
TE 24a-6 (10/79)
ROADWAY CHARACTERISTICS
Excellent - Essentially level and tangent, with no intersections, and excellent sight distance throughout.
Good - Minor curves and/or grades with sight distance above standard throughout; or few intersections, all Class A and all with good approach sight distance; or both.
Average - Moderate curves and/or grades with sight distance, if limited, not a predominant factor; or intersections which are a factor because of importance, number or poor sight distance; or both.
Adverse - Substantial curves and/or grades with limited sight distance a significant factor; or intersections which are a predominant factor because of importance, number or poor sight distance; or both.
Poor - Severe curves and/or grades requiring definitely reduced speed, with limited sight distance a dominant factor; or numerous or important intersections with poor sight distance; or both.
SHOULDERS
Good - Stable shoulder, generally 6 feet or wider.
Average - Stable shoulder, generally 2 feet to 6 feet wide.
Poor - Stable shoulder less than 2 feet wide;
Unstable shoulder of any width
Curbed section.