Warrants of Traffic Signals

Abstract

Traffic signals are like a piano. Well-tuned and on trained hand, beautiful music flows. However, improperly handled and on untrained hand, agitation and dissatisfaction frequently occur. Due to its nature of restrictive control, signalization has been widely viewed as the universal solution to intersection problems. When traffic signal control is justified and properly designed, it may achieve orderly traffic movement, reduce the frequency of certain types of accidents, and coordinate continuous flow of traffic. However, unjustified, poorly designed, or improperly operated traffic signals may reduce movement efficiency by increasing the frequency and severity of some types of accidents, reducing intersection capacity, producing excessive intersection delay, and encouraging disobedience to signal indications. The focus of this chapter is the need studies that warrant intersection signalization, while the rest of the book deals with traffic signal design to ensure safe and efficient traffic movement.

End-of-Chapter Problems

Hour	EB	WB	NB	SB
1	30	30	25	25
2	30	30	50	50
3	50	50	75	100
4	50	50	150	150
5	75	100	250	200
6	100	250	400	300
7	125	400	500	350
8	150	450	500	350
9	200	375	450	300
10	250	300	200	200
11	200	300	150	150
12	150	150	150	150
13	100	100	150	150
14	100	100	150	200
15	100	75	150	200
16	250	100	200	250
17	325	125	350	250
18	375	150	400	300
19	400	150	350	450
20	425	150	350	450
21	325	100	200	200
22	150	75	100	100
23	100	50	50	50
24	50	25	50	50

• 1. Given the intersection and data in this problem, determine whether the data support each of the signal warrants. For each warrant, indicate whether the warrant is:

  • (a) met

  • (b) not met

  • (c) not applicable

  • (d) insufficient information to assess.

  In the end, based on the above, indicate:

  • (a) whether a signal is warranted,

  • (b) the type of signalization that should be considered, and

  • (c) whether pedestrian signals and/or push buttons are recommended.

    In all cases, assume that no warrants are met for the hours that are not included in the study data.

    

    Note:

    Area Population: 75,000

    Approach Speeds: 35 mi/h

    Four-way STOP Control in place.

• 2. The intersection of Huntington Rd and Breckenridge Rd in Hadley, MA is under analysis for signalization. The figure below shows the location of the intersection and the next figure is a satellite image of the intersection. Currently, the intersection is controlled by four-way STOP signs. However, traffic demand as well as crash history at this location may warrant intersection signalization. As a transportation engineering professional, you are asked to conduct a signal warrant analysis study for the town.

  

  

  The following data were obtained from field data collection:

  • (a) Traffic counts on an average day are listed in the table below. Note that the posted speed limit is 30 mph on major street and the intersection lies within the built-up area of an isolated community having a population of less than 10,000.

    Time	Major St EB	Major St WB	Major St total	Minor St higher
    07:00 AM–08:00 AM	455	457	912	268
    08:00 AM–09:00 AM	422	408	830	218
    09:00 AM–10:00 AM	341	290	631	146
    10:00 AM–11:00 AM	323	258	580	165
    11:00 AM–12:00 PM	355	264	619	322
    12:00 PM–01:00 PM	417	276	693	152
    01:00 PM–02:00 PM	395	295	690	144
    02:00 PM–03:00 PM	394	291	684	183
    03:00 PM–04:00 PM	470	362	831	245
    04:00 PM–05:00 PM	588	433	1021	381
    05:00 PM–06:00 PM	629	440	1069	270
    06:00 PM–07:00 PM	404	359	763	164

    1. Note: 04:00–05:00 PM is peak hour

  • (b) Crashes reported by the County Sheriff’s Office and State Patrol were assessed for the 3-year period starting January 1, 2017 and ending December 31, 2019.

    Year	Angle	Rear-end
    2017	4	0
    2018	4	2
    2019	4	3

  • (c) Pedestrians crossing major street on the same day as above.

    Time	Pedestrians
    07:00 AM–08:00 AM	10
    08:00 AM–09:00 AM	44
    09:00 AM–10:00 AM	82
    10:00 AM–11:00 AM	45
    11:00 AM–12:00 PM	19
    12:00 PM–01:00 PM	34
    01:00 PM–02:00 PM	89
    02:00 PM–03:00 PM	87
    03:00 PM–04:00 PM	39
    04:00 PM–05:00 PM	76
    05:00 PM–06:00 PM	58
    06:00 PM–07:00 PM	88

  • (d) Hadley Middle School is located in this area and there are 15 schoolchildren crossing major street during the highest crossing hour on the same average day as above. A field study has been conducted during the 30-min period when the schoolchildren are using the crossing, and found that 35 adequate gaps are available during that period. Currently, schoolchildren cross the street on their own without any other remedial measures.

  • (e) Since the intersection is located in an isolated area, it is not in coordination with any other traffic signals.

  • (f) There is no railroad grade crossing near the intersection.

    Given the intersection and data in this problem, determine whether the data support each of the signal warrants. For each warrant, indicate whether the warrant is:

  • (a) met

  • (b) not met

  • (c) not applicable

  • (d) insufficient information to assess.

    In the end, based on the above, indicate:

  • (a) whether a signal is warranted,

  • (b) the type of signalization that should be considered, and

  • (c) whether pedestrian signals and/or push buttons are recommended.

    In all cases, assume that no warrants are met for the hours that are not included in the study data.

• 3. Determine if the intersection described below justifies installation of a traffic signal based on the traffic volume criteria for Warrant 1, conditions A and B.

  • (a) Major St. has two lanes in each direction

  • (b) Minor St. has one lane per direction

  • (c) Located in suburb of a major metropolitan area

  • (d) Speed limit on both roads is 45 mph

    Identify how many hours are met for each warrant and clearly state your recommendations.

    Time	Major St.	Minor St.
    6–7 AM	764	139
    7–8 AM	825	161
    8–9 AM	985	76
    9–10 AM	976	56
    10–11 AM	768	63
    11–12 NOON	904	158
    12–1 PM	689	123
    1–2 PM	645	175
    2–3 PM	706	188
    3–4 PM	928	178
    4–5 PM	943	197
    5–6 PM	950	153
    6–7 PM	910	142