Test 18 - Traffic Signal Fundamentals

Question 1 ప్రశ్న 1

A four-leg urban intersection experiences heavy conflicting traffic movements during peak periods. What is the principal traffic-engineering function of installing a properly designed traffic-signal system?

A To eliminate all merging and diverging conflicts without modifying traffic movements. B To allocate right of way to conflicting movements in an orderly sequence of timed indications. C To guarantee uninterrupted movement on every approach regardless of conflicting traffic. D To replace the need for intersection visibility, road markings and pedestrian facilities.

Question 2 ప్రశ్న 2

At a conventional three-aspect traffic signal, which interpretation of the steady red, steady amber and steady green indications is technically correct?

A Red permits movement after slowing, amber gives unrestricted priority, and green requires vehicles to stop. B Red prohibits only turning movements, amber permits acceleration, and green applies only to through traffic. C Red and amber both permit entry whenever no other vehicle is visible, while green requires compulsory stopping. D Red requires stopping, amber warns of the impending termination of the permitted movement and requires stopping where this can be done safely, and green permits movement subject to applicable conflicts and safety requirements.

Question 3 ప్రశ్న 3

A signal controller provides a period of right of way to a selected group of compatible traffic movements, followed by changes in the displayed signal indications. Which statement correctly distinguishes a signal phase from a signal interval?

A A phase is a controller timing unit serving one or more movements, whereas an interval is a period during which the relevant signal indications remain unchanged. B A phase is always the amber period, whereas an interval is the complete signal cycle. C A phase represents only one traffic lane, whereas an interval always represents an entire intersection. D A phase is the period during which all signals are red, whereas an interval is the time between successive intersections.

Question 4 ప్రశ్న 4

A fixed-time two-phase signal operates with the following nonoverlapping successive intervals: Phase 1 has 30 seconds of green, 3 seconds of amber and 2 seconds of all-red clearance; Phase 2 has 25 seconds of green, 4 seconds of amber and 2 seconds of all-red clearance. What is the complete cycle length?

A 55 seconds. B 62 seconds. C 66 seconds. D 70 seconds.

Question 5 ప్రశ్న 5

An isolated intersection operates under a pre-timed traffic-signal plan with fixed green, amber and red-clearance intervals. Which operating characteristic identifies this as fixed-time control?

A Every green interval terminates only when a vehicle detector reports an acceptable gap. B The programmed signal sequence and interval durations follow a predetermined timing plan rather than changing in response to individual vehicle detections. C All approaches receive green continuously until pedestrians request service. D The controller changes its phase sequence randomly to prevent repetitive traffic queues.

Question 6 ప్రశ్న 6

A signalized junction has a heavily travelled major road and a lightly travelled minor road. Detectors on the minor-road approaches request and influence the duration of minor-road service, while the major road generally retains green when there is no conflicting demand. Which control strategy best describes this arrangement?

A Semi-actuated signal control. B An entirely fixed-time signal with no detector influence. C An unsignalized priority-controlled intersection. D A fully grade-separated traffic interchange.

Question 7 ప్రశ్న 7

A traffic-signal installation has vehicle detectors on all approaches, and the controller determines the occurrence and duration of vehicle phases in response to detected demand and programmed timing constraints. What is this control strategy called?

A Fixed-time control without traffic detection. B Manual traffic control. C Uncontrolled intersection operation. D Fully actuated signal control.

Question 8 ప్రశ్న 8

Several signalized intersections along an urban arterial are coordinated so that vehicle platoons can pass successive intersections with fewer stops. What is the principal function of the signal offset in this coordination?

A To specify the minimum amber duration at every intersection independently of traffic demand. B To determine the saturation headway of individual vehicles. C To establish the time relationship between defined reference points in the cycles of coordinated intersections. D To eliminate the need for a common or compatible cycle relationship.

Question 9 ప్రశ్న 9

At a signalized intersection, engineers provide both an amber change interval and a following all-red clearance interval during a phase transition. Which statement most accurately describes their different functions?

A Amber warns of termination of the permitted movement, while all-red provides a period in which the relevant conflicting movements remain stopped to allow clearance. B Amber provides exclusive pedestrian crossing time, while all-red is an additional green interval for vehicles. C Amber eliminates start-up lost time, while all-red increases saturation flow rate. D Amber and all-red are identical indications and must always have equal durations.

Question 10 ప్రశ్న 10

A specified signal phase transition consists of 3 seconds of amber followed immediately by 2 seconds of all-red clearance. If the intergreen period is defined for this exercise as the sum of these two consecutive intervals, what is its duration?

A 2 seconds. B 5 seconds. C 3 seconds. D 6 seconds.

Question 11 ప్రశ్న 11

In signal-capacity analysis, which statement correctly distinguishes start-up lost time from clearance lost time?

A Start-up lost time occurs only during red, while clearance lost time is identical to the complete displayed green. B Start-up lost time is the entire pedestrian crossing time, while clearance lost time is the cycle length. C Start-up lost time reflects inefficient initial discharge as queued vehicles react and accelerate, while clearance lost time represents the unusable portion associated with the change and clearance intervals. D Both lost times are defined as the time during which vehicles discharge at the full saturation flow rate.

Question 12 ప్రశ్న 12

For a signal phase, the displayed green is 28 seconds, amber is 3 seconds and all-red clearance is 2 seconds. The start-up lost time is 2 seconds and clearance lost time is 2 seconds. Using the explicitly adopted relation g = G + Y + R - l1 - l2, what is the effective green time?

A 27 seconds. B 31 seconds. C 33 seconds. D 29 seconds.

Question 13 ప్రశ్న 13

A simplified two-phase signal has a cycle length of 80 seconds and a total lost time of 8 seconds per cycle. Assuming the phases are served sequentially with no overlapping critical-phase accounting, what is the total effective green time available for allocation between the two phases?

A 72 seconds. B 80 seconds. C 64 seconds. D 88 seconds.

Question 14 ప్రశ్న 14

A movement at a signalized intersection has an effective green time of 30 seconds in a 75-second cycle. What is its effective green ratio?

A 0.30. B 0.45. C 0.40. D 2.50.

Question 15 ప్రశ్న 15

After the initial start-up period, queued vehicles discharge through a signalized lane at an approximately uniform saturation headway of 2.4 seconds per vehicle. What is the corresponding saturation flow rate per lane?

A 1200 vehicles/h. B 1500 vehicles/h. C 1800 vehicles/h. D 2400 vehicles/h.

Question 16 ప్రశ్న 16

A signalized lane group has a saturation flow rate of 1800 vehicles/h, an effective green time of 30 seconds and a cycle length of 90 seconds. Using c = s(g/C), what is its estimated capacity?

A 450 vehicles/h. B 900 vehicles/h. C 1800 vehicles/h. D 600 vehicles/h.

Question 17 ప్రశ్న 17

A signalized lane group has a traffic demand of 540 vehicles/h and an estimated capacity of 600 vehicles/h under the existing timing plan. What is its volume-to-capacity ratio?

A 0.75. B 0.90. C 1.11. D 1.50.

Question 18 ప్రశ్న 18

The critical lane group of a signal phase carries 600 vehicles/h and has a saturation flow rate of 1800 vehicles/h. What is its traffic flow ratio y = q/s?

A Approximately 0.333. B 0.600. C 1.200. D 3.000.

Question 19 ప్రశ్న 19

A simplified two-phase signal analysis identifies critical flow ratios of 0.25 and 0.35 for the two sequential phases. What is the sum of the critical flow ratios used in a conventional two-phase signal-timing calculation?

A 0.10. B 0.35. C 0.60. D 1.40.

Question 20 ప్రశ్న 20

A fixed-time two-phase signal has 70 seconds of total effective green available. The critical flow ratios are 0.30 for Phase 1 and 0.20 for Phase 2. If effective green is allocated in proportion to these critical flow ratios, what are the two allocations?

A 35 seconds and 35 seconds. B 30 seconds and 20 seconds. C 40 seconds and 30 seconds. D 42 seconds and 28 seconds.

Question 21 ప్రశ్న 21

A queue of 12 vehicles must discharge through a continuously green signalized lane. Assume a saturation headway of 2 seconds per vehicle and a start-up lost time of 2 seconds. Using the simplified relation T = l1 + Nh, what is the time required for the complete queue to discharge?

A 26 seconds. B 24 seconds. C 22 seconds. D 28 seconds.

Question 22 ప్రశ్న 22

At a signalized four-leg intersection operating under left-hand traffic, right-turning vehicles experience frequent conflicts with opposing through traffic. Which statement correctly distinguishes protected right-turn operation from permissive right-turn operation?

A Protected right turns require vehicles to accept gaps in the opposing through stream, whereas permissive right turns remove that conflict. B Protected right turns use signal control to separate the right-turn movement from conflicting opposing traffic in time, whereas permissive right turns rely on drivers yielding and accepting suitable gaps. C Both protected and permissive right turns necessarily operate without any signal indications. D Permissive right turns require grade-separated ramps, whereas protected right turns require a rotary.

Question 23 ప్రశ్న 23

A busy urban intersection has a substantial pedestrian crossing movement that conflicts with a proposed simultaneously operating protected vehicle-turning movement. Which phasing decision is most appropriate?

A Give both movements unrestricted simultaneous right of way because pedestrians can always avoid the vehicles. B Increase the turning speed so that the conflicting vehicles occupy the crossing for less time. C Remove pedestrian signal indications without assessing pedestrian demand or crossing time. D Arrange the signal phases or movement controls so that the identified incompatible pedestrian and vehicle movements are appropriately separated.

Question 24 ప్రశ్న 24

In actuated signal control, an active phase has completed its minimum green and receives no further detector calls within the specified passage-time interval, while another phase is requesting service. Which statement correctly identifies this termination mechanism and distinguishes it from max-out?

A It is max-out because every actuated phase ends only after reaching its maximum green. B It is pre-timed termination because detector information does not influence the phase. C It is gap-out because the relevant detection gap has expired; max-out instead refers to termination upon reaching the applicable maximum green under the required conditions. D It is all-red clearance because the minimum green interval has ended.

Question 25 ప్రశ్న 25

A metropolitan traffic-control centre receives continuous detector data from several coordinated intersections and adjusts signal splits, cycle lengths and offsets in response to changing traffic conditions. Which statement best describes this strategy?

A It is a purely fixed-time plan that cannot change until an engineer manually rewrites all signal timings. B It is an uncontrolled intersection arrangement because detectors replace the signal indications. C It is necessarily the same as isolated semi-actuated operation at a single minor-road approach. D It is adaptive or traffic-responsive network signal control, which adjusts timing parameters using measured traffic conditions.

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