Transport Engineering (CENG 3101) Chapter 5: Traffic Management and Control PDF

DEPARTMENT OF CIVIL ENGINEERING Transport Engineering (CENG 3101) CHAPTER 5: TRAFFIC MANAGEMENT AND CONTROL 5.1 Traffic Marking, Signs At the end of this chapter, 5.2 Traffic Signals students will be able to  Design road furniture and...

DEPARTMENT OF CIVIL ENGINEERING Transport Engineering (CENG 3101) CHAPTER 5: TRAFFIC MANAGEMENT AND CONTROL 5.1 Traffic Marking, Signs At the end of this chapter, 5.2 Traffic Signals students will be able to  Design road furniture and traffic signal timing applying Software’s By Haile G. Nov 2024  Introduction  The movement of people, goods, vehicles, trains, ships, and airplanes from one place to another is called traffic.  Controlling traffic involves attempts to make these movements as fast, safe, and efficient as possible.  Traffic control devices are markers, signs and signal devices used to inform, guide and control traffic, including pedestrians, motor vehicle drivers and bicyclists.  These devices are usually placed adjacent, over or along the highways, roads, traffic facilities and other public areas that require traffic control.  Introduction  Traffic control devices are the media by which traffic engineers communicate with drivers.  Traffic markings  Traffic signs  Traffic signals  Purpose: To help ensure road safety by providing for the orderly and predictable movement of all traffic.  Cont…. 4  Introduction 5 Messages are conveyed through the use of: Color  It is the most easily visible characteristic of a device; red, yellow, green, orange, black, blue, and brown Shape:  After color, the shape of the device is the next element to be discerned by the driver  Introduction 6 Pattern:  It is used in the application of traffic markings.  In general, double solid, solid, dashed, and broken lines are used Legend:  The last element of a device that the driver comprehends is its specific legend.  Signals and markings  Introduction 7  cont.… 8  Colors 9  GREEN: Guide, directional information.  RED: Stop, do not enter or wrong way.  BLUE: Motorist services guidance Also used to identify parking spaces for disabled drivers.  ORANGE: Construction and maintenance.  BROWN: Public recreation areas and scenic guidance  YELLOW: General warning.  WHITE: Regulatory.  BLACK: Regulatory  Shapes 10  Shapes 11  Cross buck: Railroad crossing  Octagon: STOP  legend 12  Traffic Markings 13  Longitudinal markings  Transverse markings  Object markers and delineators 1. Longitudinal markings are those markings placed parallel to the direction of travel involve centerlines, lane lines, and pavement edge lines.  Provide for organized flow and optimal use of the pavement width.  Centerlines 14  Separates the opposing streams of traffic and facilitates their movements.  The centre line may be marked with  Single broken line,  Single solid line,  Double broken line, or double solid line depending upon the road and traffic requirements  Centerlines 15  A double-solid yellow center marking indicates that passing is not permitted in either direction.  A solid yellow line with a dashed yellow line indicates that passing is permitted from the dashed side only.  Passing is permissible in both directions; a single dashed yellow centerline is used  Lane Markings 16  The typical lane marking is a single white dash line separating lanes of traffic in the same direction.  Standards recommends lane markings on  All free ways,  Interstate highways and  All highways with two or more adjacent traffic lanes in a single direction.  Lane mark 17  Cont… 18  Cont… 19  The dashed lane line indicates that lane changing is permitted.  A single solid white lane line indicate that lane- changing is discouraged but not illegal.  Where lane-changing is to be prohibited, a double- white solid lane line is used.  Edge Markings 20  Indicate edges of rural roads which have no curbs to delineate the limits up to which the driver can safely venture.  At least 150 mm from the actual edge.  They are painted in yellow or white lines should be preferably light reflective using minute glass beads embedded  Edge 21  Warning lines 22  Warn the drivers about the obstruction approaches  Marked on horizontal and vertical curves where the visibility is greater than prohibitory criteria specified for no overtaking zones.  Broken lines with 6 m length and 3 m gap  Warning 23  Warning lines 24  Warning lines 25  Cont… 26  Transverse Markings 27  Include any and all markings with a component that cuts across.  All transverse markings are white.  Crosswalk Markings (zebra) 28  Crosswalks be marked at all intersections with "substantial" conflict between vehicles and pedestrian exists  Identify the crosswalk is another option used at locations with heavy pedestrian flows  Parking Space Markings 29  Parking space markings are not purely transverse, as they contain both longitudinal and transverse elements  officially categorized as transverse markings  Cont… 30  Directional arrows 31  Directional arrows used to guide the drivers in advance over the correct lane to be taken while approaching busy intersections.  Directional arrows 32  Word and Symbol Markings 33  Word markings include "ONLY" used in conjunction with lane use arrows,  "STOP" which can be used only in conjunction with a STOP line and a STOP sign.  "SCHOOL" markings are often used in conjunction with signs to demark school and school-crossing zones  Object Markers 34  Object markers are used to denote obstructions either or adjacent to the traveled way  There are three four of object markers  Use object markers to mark obstructions within or adjacent to the roadway. There are four types of object markers, Type 1, Type 2, Type 3, and Type 4.  Obstructions within the roadway must be marked using a Type 1 or Type 3 marker.  Type 3 markers shall have stripes pointed downward on the side traffic should pass.  Object Markers 35  Objects adjacent to the roadway should be marked with Type 2 or Type 3 markers.  These include underpass piers, bridge abutments, handrails, and culvert headwalls. In some cases they may be used to mark roadside conditions such as narrow shoulder drop-offs, gores, small islands, and abrupt changes in roadway alignment.  The Type 4 object marker is used to warn and alert road users of the end of a roadway.  Object Markers 36  Object Markers 37  Type-1  Nine yellow retro reflectors  3-in minimum diameter on a yellow or black diamond panel  18 in or more on a side;  or an all-yellow retro reflective diamond panel of the same size.  Object Markers 38  Type-2  Three yellow retro reflectors  3-in minimum diameter arranged horizontally or vertically on white panel  at least 6 X 12 in;  or an all yellow retro reflective panel of the same size  Object Markers 39  Type-3  A striped marker measuring 12 X 36 in  alternating black and yellow stripes sloping downward  at an angle of 45° toward the side of the obstruction on which traffic is to pass.  Object Markers 40  Type-4  It is used to warn and alert road users of the end of a roadway in other than construction or maintenance areas.  Standard.  If object markers are used to mark the end of a roadway, four Type 4 object marker shall be used.  Traffic Signs 41 Fall into three major categories:  Regulatory signs.  Warning signs.  Guide signs.  Regulatory Signs 42 1. Regulatory (Traffic lanes or regulations) (Speed limit and stop sign, yield, no right-turn, one-way, no parking) stop sign, yield, no right turn, one way, no parking) 2. Warning (Curve signs,) own safety 3. Guide signs ( directions, distances, restaurant etc.)  Regulatory Signs 43  Used to inform road users of selected traffic laws or regulations  Indicate the applicability of the legal requirements.  Convey information concerning right-of-way, speed limits, lane usage, parking, or a variety of other functions  Regulatory Signs 44  Except for some special signs, such as the STOP and YIELD sign, most regulatory signs are rectangular, with the long dimension vertical.  Some regulatory signs are square  The background color of regulatory sign is white, while legend or symbols are black.  In symbol signs, a red circle with a bar through it signifies a prohibition of the movement indicated by the symbol.  Right of Way Series and Speed series 45  Right of Way Series Two unique signs;  STOP sign at the stop line  GIVE WAY sign and is Common when one minor road and major road meets at an intersection.  Speed series  Used to limit the speed of the vehicle on the road  Speed limit signs, truck speed, minimum speed signs  Movement series 46  Signs that affect specific vehicle maneuvers  Turn signs, alignment signs, exclusion signs, one way signs  Turn signs include turn prohibitions and lane use control signs  Lane use signs make use of arrows to specify the movements  Turn signs are used to safely accommodate turns in un signalized intersections  Parking Series and Pedestrian series 47  Parking Series  Indicates parking prohibitions or restrictions, places where parking is permitted, the type of vehicle to be parked, duration for parking Pedestrian series  Both legend and symbol signs.  For the safety of pedestrians  Include signs indicating pedestrian only roads, pedestrian crossing sites  Miscellaneous 48  Signs that are included in this category are:  "KEEP OF MEDIAN" sign,  Signs indicating road closures,  Signs restricting vehicles carrying hazardous cargo or substances,  Signs indicating vehicle weight limitations  Miscellaneous 49  Stop,  No right turn,  Give way,  Vehicle width,  No entry,  Speed limit  Warning Signs 50  Call attention to unexpected conditions adjacent to a highway or street and  To situations that might not be readily apparent to road users  Alert road users to conditions that might call for a reduction of speed  Or an action in the interest of safety and efficient traffic operations  Warning Signs… 51  Mostly diamond-shaped, with black lettering or symbols on a yellow background  A pennant shape is used for the "No Passing Zone" sign  A rectangular shape is used for some arrow indications  A circular shape is used for railroad crossing warnings  Warning Signs 52  Used only to alert drivers of conditions that they could not be normally expected to discern on their own.  Overuse of warning signs encourages drivers to ignore them  Warning Signs 53  Generally, used to inform drivers  Changes in horizontal alignment  Intersections  Advance warning of control devices  Converging traffic lanes  Narrow roadways  Changes in highway design  Grades  Roadway surface conditions  Railroad crossings  Right hand curve sign board, narrow road,  Railway track ahead  Guide/Informative/ Signs 54  Provide information concerning destinations, available services  Historical/recreational facilities  Directional or destination information is provided by signs with a green background  Information on services is with a blue background  Cultural, historical, and/or with a brown back ground  Guide/Informative/ Signs 55  Guide/Informative/ Signs 56  The MUTCD provides guide-signing information for three types of facilities:  Conventional roads, freeways, and expressways  Guide signing is somewhat different from other types in that overuse is generally not a serious issue, unless it leads to confusion  Guide/Informative/ Signs 57  Route markers, destination signs, mile posts, service centre  Traffic signal 58  Traffic lights consist normally of three signals, transmitting meaningful information to drivers, riders and pedestrians through colors and symbols.  The regular traffic light colors are red, yellow, and green arranged vertically or horizontally in that order.  The operation of signalized intersections is often complex, involving competing vehicular and pedestrian movements.  Objectives of Signal Timing 59  To reduce the average delay of all vehicles and the probability of accidents  To move people through an intersection safely and efficiently  Traffic Signal Operations 60  Components of a Signal Cycle 61 The most fundamental unit in signal design and timing is the cycle 1. Cycle  A signal cycle is one complete rotation through all of the indications provided 2. Cycle length: is the time (in seconds) that it takes to complete one full cycle of indications. symbol "C.“ 3. A traffic phase is defined as the green, change, and clearance intervals in a cycle assigned to specified movement(s) of traffic.  Cont… 62 4. Interval.  The interval is a period of time during which no signal indication changes.  It is the smallest unit of time described within a signal cycle  Cont… 63 Types of intervals within a signal cycle: a) Change interval (Yellow Time) or (Yellow Change)  The change interval is the "yellow" indication for a given movement. It is part of the transition from "green" to "red,”  The change interval is given the symbol “ti” for movement(s) i.  It is timed to allow a vehicle that cannot safely stop when the "green" is withdrawn to enter the intersection legally  Warn drivers of end of phase  The main purpose of the yellow indication after the green is to alert motorists  A bad choice of yellow interval may lead to the creation of a dilemma zone  Cont… 64 (b) Clearance interval( All Red /Red Clearance)  The clearance interval is also part of the transition from "green" to "red" for a given set of movements.  All movements have a "red" signal  It is timed to allow a vehicle that legally enters the intersection on "yellow" to safely cross the intersection before conflicting flows are released  Cont… 65  It is timed to allow a vehicle that legally enters the intersection on "yellow" to safely cross the intersection before conflicting flows are released  Is given the symbol "ari” (for "all red") for movement(s) i.  R = all-red clearance interval (sec)  S = vehicle speed (fps)  W = distance from stop line to intersection far side (ft)  L = vehicle length (ft)--- 20 ft for passenger cars  Cont… 66 (c) Green interval  Each movement has one green interval during the signal cycle  Is given the symbol "Gi” for movement(s) i. (d) Red interval  Each movement has a red interval during the signal cycle  The red interval is given the symbol "Ri” for movement(s) i.  Cont… 67 (e) Offset:  The time lapse in seconds or the percentage of the cycle length between the beginning of a green phase at an intersection and the beginning of a corresponding green phase at the next intersection.  Cont… 68  Cont… 69 ……….…………………5.1 5.1 ………………….…………5.2 Example  Phase(Signal Phasing) 70 Phase:  Is the green interval plus the change and clearance intervals that follow it. Thus, during green interval, non conflicting movements are assigned into each phase. It allows a set of movements to flow and safely halt the flow before the phase of another set of movements start.  A signal phase consists of  A green interval,  The change and  Clearance intervals that follow it.  Allows a designated movement or set of movements to flow and to be safely halted before release of a conflicting set of movements.  Cont… 71  Cont.…. 72  Cont.… 73  Phase Plans 74 Permitted LT Protected LT  Phase 75  Two phase 76  Exclusive left turn phasing 77  Leading and Lagging Green phase 78  Exclusive left turn phase with leading green 79  Criteria for Left Turn Phasing 80 For LT Protected 81  Determining sum of critical lane Volumes 82  It is per lane volume that controls the required length of a particular phase.  Through vehicle Equivalent factors 83  Exclusive pedestrian phase 84  T intersection 85  Cont… 86  Split-phase Is the part of a phase that is set apart from the primary movement, thus forming a special phase that relates to the parent phase.  Peak-hour factor (PHF) A measure of the variability of demand during the peak hour.  PHF= Volume during peak hour/4*volume during peak 15 min within peak hour  DHV= Peak hour volume/PHF Example: Determining the Peak-Hour Factor and the Design Hourly Volume at an Intersection  Total volume during peak hour  = (375 +380+ 412+ 390) =1557  Peak Volume during peak 15 min = 412  Cont…. 87  Lane group: A lane group consists of one or more lanes on an intersection approach and having the same green phase.  Critical lane group: The lane group that requires the longest green time in a phase  Saturation flow rate: The flow rate in veh/h that the lane group can carry if it has the green indication continuously  The saturation flow rate(s) depends on an ideal saturation flow (so), which is usually taken as 1900 veh/h of green time per lane (Ideal average headway of 3600/1900= 1.895 sec).  Typical Lane Groups for Analysis and Traffic Flow at Signalized Intersections 88  Lost Time & Effective Green Time 89 90  Erfe 𝑇= GREEN time required to move queue of “n" vehicles through a signalized intersection  Saturation Flow and Capacity (HCM Method) 91  Methods to determine the optimum cycle length 92  Several design methods have been developed to determine the optimum cycle length, two of which the Webster and the HCM methods are common.  Webster Method: …………………………………5.3  Optimum, Desired and Minimum Cycle Length 93  Total Lost Time 94 ………………………………5.4 ………………………………5.5  Cont… 95  Allocation of green times 96 ………………………………5.6 …………………………………5.7 …………………………………5.8  Minimum Green Time (Minimum Pedestrian Green Time) 97  At an intersection where a significant number of pedestrians cross, it is necessary to provide a minimum green time that will allow the pedestrians to safely cross the intersection.  The minimum pedestrian green time for a phase is determined based on typical values of pedestrian walking speed (4 ft/sec or 3.5/ft/sec)  Cont… 98 …………………5.9 …………………5.10  Key elements of signal design and timing 99  Signal design procedures 100  The signal design procedure involves six major steps. They include; 1. Phase design, 2. Determination of amber time and clearance time, 3. Determination of cycle length, 4. Apportioning of green time, 5. Pedestrian crossing requirements, and 6. The performance evaluation of the above design.  Example 101 1. The phase diagram with flow values of an intersection with two phases is shown in figure below. The lost time and yellow time for the first phase is 2.5 and 3 seconds respectively.  For the second phase the lost time and yellow time are 3.5 and 4 seconds respectively. If the cycle time is 120 seconds, find the green time allocated for the two phases.  Solution 102  Example 103 2. Figure below shows peak-hour volumes for a major intersection on an expressway. Using the Webster method, determine a suitable signal timing for the intersection using the four-phase system shown below. Use a yellow interval of 3 seconds and the saturation flow given. Note: The influence of heavy vehicles and turning movements and all other factors that affect the saturation flow have already been considered. 222 928 642 128 25 352 184 306  Solution 104  Determine equivalent hourly flows by dividing the peak-hour volumes by the PHF (e.g., for left-turn lane group of phase A, equivalent hourly flow 222/0.95 = 234). See Figure below for all equivalent hourly flows. Compute the total lost time. Since there is not an all-red phase—that is, R= 0 and there are four phases, Solution 105 ΦA 32 3 65 ΦB 35 22 3 40 ΦC 60 7 3 30 ΦD 70 27 3 C=100