Basic Design Review Fall 2017 A few slides were taken from CVEN 307 originally prepared by Dr. Gene H. Hawkins.

Basic Principles Road Network: Carries motorized and non-motorized traffic. Is part of the overall transportation network, which includes rail, waterways and aviation. Plays an essential part in developing urban and rural areas. The task of road network design is to arrange and design individual road sections according to their respective functions within the scope of transportation and regional planning. Traffic related functions (mobility/access) versus non- traffic related functions (local/pedestrian use).

Historical Perspective • Oldest known highway: The Faiyumhollow located 70 km south of Cairo, Egypt (4,600 BC). This was 13-km road (naturally paved) linking a quarry to the Nile. • The Greeks were the first to establish “law of road construction” setting minimum vehicle track width at 4ft-4in. • First paved roads were called procession roads located near temple and holy places. Some were designed with tracks for the movements of wagons.

Historical Perspective • Early road networks: Trade and Religious Military: * Extensive, fast relocation of armies to quell rebellions * Easily spreading important news throughout the empire * Safe and effective transport of tributes from conquered nations.

Historical Perspective • Romans: * Road construction and design were very advanced (400,000 km at its height of power; 80,00 km of excellent quality) *Straight and elevated, if possible (to dominate the surroundings) * 10% maximum grade * Did their design affected current traffic fatalities in London?

Historical Perspective Romans’ highway network illustrated as a subway map http://sashat.me/wp-content/uploads/2017/06/roman_roads_24_jun.png

Historical Perspective • In 1835, lectures about road construction trackage engineering were part of the engineering program at University of Karlsruhe (new name). • In 1887, Launhartd wrote the “Theory of the Alignment”, which included a discussion about circular curves. • In 1920, Euting wrote “The Construction of Rural Roads”. This manual include information maximum grades for different types of terrain and cross-sections.

Wright and Dixon (2004) Figure 1-3

Role of Highways The two considerations in classifying highway and street networks functionality are 1) travel mobility and 2) access to property Mobility: To provide users with means to travel from a point of origin to a point of destination the most efficient and safest way possible Access: To provide users access to services and property the most efficient way possible

Road Functions Roads serve one of two functions Basis for design Mobility (higher class) Access (lower class) Cannot serve both functions well Basis for design Design for function, not volume Very important!

Wright and Dixon (2004) Figure 1-2

Maze et al. (2000) Figure 5

Factors that Affect Design Vehicles Type of Vehicle Proportion in Traffic Stream Driver Older Drivers Roadway Volume Speed Features Vehicles Planes, trains, autos, buses, ships, trucks Infrastructure Road, canal, rail, air Transfer points Supporting elements (signs, signals, safety) Operators/Content Drivers, pilots, freight, passengers

Design Process STEPS EXAMPLES PROCESS Freeway vs Arterial Tollway Express vs Local Transit Type of Facility Planning Size of Facility Traffic Design # of Lanes # of Runways Alignment Configuration/Orientation Environmental Impact Assessment Preliminary Design Location

Design Process (Cont.) STEPS EXAMPLES PROCESS Design Speed Design Vehicle Design Driver Identify Standards Physical Design Plans, Specification, & Estimates (PS&E) Physical Design Geometric Features Surface/Guideway Design Auxiliary Systems Construction Materials Structures Construction

Wright and Dixon (2004) Fig 13-1

Speed Definitions Design Speed – a selected speed used to determine the various geometric features of the roadway. The assumed design speed should be a logical one with respect to the topography, anticipated operating speed, the adjacent land use, and the functional classification of the highway. Operating Speed – speed of vehicles in free flow conditions Space mean speed (distance/time) Running Speed – speed at which vehicle travels over a highway section Time mean speed (spot speed over time) Posted Speed – speed limit 85th percentile of time mean speed (in theory)

Design Controls Vehicles Drivers Dimensions Driving Task Performance Guidance Task Pollution Driver Expectancy

Stopping Sight Distance Definition: The available sight distance on a highway that allows a vehicle traveling near the design speed to stop before reaching a stationary object in its path Brake Reaction Time (d1) Braking Distance (d2)

Passing Sight Distance Definition: The sight distance needed for allowing a faster vehicle to pass a slower vehicle on a two-lane highway Sum of four distances: d1 – Distance traversed during the perception and reaction time + acceleration to the point of encroachment d2 – Distance traveled while the passing vehicle occupies the left lane d3 – Distance between the passing vehicle at the end of its maneuver and the opposite vehicle d4 – Distance traversed by an opposing vehicle for 2/3 of the time the passing vehicle occupies the left lane

Passing Sight Distance Initial Maneuver Distance Clearance Distance Opposing Vehicle Distance Occupying Left-Lane Distance

Passing Sight Distance 6th edition only provides values. It does not separate the analysis in 4 parts.

Horizontal Alignment

Superelevation Design Desirable superelevation: for R > Rmin Where, V= design speed in ft/s or m/s g = gravity (9.81 m/s2 or 32.2 ft/s2) R = radius in ft or m Various methods are available for determining the desirable superelevation, but the equation above offers a simple way to do it. The other methods are presented in the next few overheads.

Methods for Estimating Desirable Superelevation Superelevation and side friction are directly proportional to the inverse of the radius (straight relationship between 1/R=0 and 1/R =1/Rmin) Method 2: Side friction is such that a vehicle traveling at the design speed has all the acceleration sustained by side friction on curves up to those requiring fmax Superelevation is introduced only after the maximum side friction is used

Method 3: Method 4: Method 5: Superelevation is such that a vehicle traveling at the design speed has all the lateral acceleration sustained by superelevation on curves up to those required by emax No side friction is provided on flat curves May result in negative side friction Method 4: Same approach as Method 3, but use average running speed rather than design speed Uses speeds lower than design speed Eliminate problems with negative side friction Method 5: Superelevation and side friction are in a curvilinear relationship with the inverse of the radius of the curve, with values between those of methods 1 and 3 Represents a practical distribution for superelevation over the range of curvature This is the method used for computing values shown in Exhibits 3-25 to 3-29

Five Methods fmax e = 0 emax f M2 M1 M5 M3 1/R M4 Side Friction Factor Reciprocal of Radius 1/R M4

Superelevation Design for High Speed Rural and Urban Highways

Transition Design Control Tangent Runout

Transition Design Control Superelevation Runoff

Transition Design Control

Transition Design Control http://techalive.mtu.edu/modules/module0003/Superelevation.htm

Minimum Length of Superelevation Runoff

Minimum Length of Superelevation Runoff ∆ = relative gradient in previous overhead

Minimum Length of Superelevation Runoff Values for n1 and bw in equation

Minimum Length of Tangent Runout See Exhibit 3-32 for values of Lt and Lr

Superelevation Runoff

Vertical Curve A = G2 – G1 K = L / |A| Rate of change of grade Offset y = 4E(x/L)2 Offset External Distance E = M = A L / 800 Vertical Point of Intersection Ele. of P = [ele. Of VPC + (G1 / 100) x] + y X = L|G1|/ (|G1 – G2|) (high or low point) Vertical Point of Tangency Vertical Point of Curvature

Criteria for Measuring Sight Distance Driver Eye Height Passenger Car: 3.5 ft Large Trucks: 5.9 to 7.9 ft SSD Object 2.0 ft PSD Object 3.5 ft Object

Measuring Sight Distance

Vertical Crest Curve

Vertical Crest Curve

Vertical Sag Curve

Vertical Sag Curve

Vertical Sag Curve

Vertical Sag Curve

Vertical Sag Curve S > L:

Vertical Sag Curve S < L:

Theoretical Application of Method 5 (with example)

Selection of fdesign and edesign (Method 5) fmax (for the design speed) Side Friction Factor e = 0 fdesign emax (for the design speed) Reciprocal of Radius 1/R

Selection of fdesign and edesign Rf = V2/(gfmax) Rmin = V2/[g(fmax + emax)] fmax Side Friction Factor e = 0 fdesign emax Ro = V2/(gemax) Reciprocal of Radius 1/R R0: f = 0, e = emax

Selection of fdesign and edesign fdesign = α(1/R)+β(1/R)2 fmax (for the design speed) Side Friction Factor α = fmaxRmin[1-{Rmin/(R0-Rmin)}] e = 0 fdesign β = fmaxRmin3/(R0-Rmin) emax (for the design speed) Reciprocal of Radius 1/R

Example: Design Speed: 100 km/h fmax = 0.128 emax = 0.06 Question? What should be the design friction factor and design superelevation for a curve with a radius of 600 m?

1. Compute Rf, R0, and Rmin: Rf = V2/(gfmax) = 27.782 / (9.81 x 0.128) = 615 m R0 = V2/(gemax) = 27.782 / (9.81 x 0.06) = 1311 m Rmin = V2/[g(fmax + emax)] = 27.782 / [9.81(0.128+0.06)] Rmin = 418 m

Selection of fdesign and edesign (example) fmax = 0.128 Side Friction Factor e = 0 fdesign emax = 0.06 1 / 1311 1 / 615 1 / 418 1/R

2. Compute α and β: α = 0.128 x 418 x [1 – 418 / (1311 – 418) ] = 28.45 m β = 0.128 x 4183 / (1311 – 418) = 10,502 m2 3. Compute fdesign and edesign : First, estimate the right-hand side of equation for designing superelevation e + f = V2/(gR) = 27.782 / (9.81 x 600) = 0.131 Then, fdesign = 28.45 / 600 + 10502 / 6002 = 0.076 edesign = 0.131 – 0.076 = 0.055 (< emax = 0.06)

Selection of fdesign and edesign (example) fmax = 0.128 Side Friction Factor e = 0 fdesign emax = 0.06 0.076 1 / 1311 1 / 615 1 / 418 1/R 1 / 600

Selection of fdesign and edesign (example) R=600 ft