Cheatsheet: Transportation Planning

1. Travel Demand Forecasting

1.1 Four-Step Travel Demand Model

1.2 Trip Generation Methods

1.2.1 Trip Production and Attraction

• Productions: Home-based trips originating from residential zones
• Attractions: Trips destined to employment, shopping, or activity centers
• Balancing required: Total productions must equal total attractions

1.3 Trip Distribution Models

1.3.1 Gravity Model

T_ij = P_i × A_j × F_ij × K_ij / Σ(A_j × F_ij × K_ij)

1.3.2 Friction Factor Functions

• Exponential: F = e^-βt
• Power: F = t^-β
• Gamma: F = t^β × e^-αt
• β and α are calibrated parameters

1.4 Mode Choice Models

1.4.1 Logit Model (Multinomial)

P_n(i) = e^U_in / Σe^U_jn

• P_n(i) = Probability person n chooses mode i
• U_in = Utility of mode i for person n
• Utility function: U = β₁X₁ + β₂X₂ + ... + β_nX_n

1.4.2 Mode Choice Factors

• Travel time (in-vehicle and out-of-vehicle)
• Travel cost (fare, fuel, parking)
• Comfort and convenience
• Safety and reliability
• Auto ownership and availability
• Trip purpose (work, shopping, recreation)

1.5 Trip Assignment Methods

1.5.1 Bureau of Public Roads (BPR) Function

t = t₀[1 + α(v/c)^β]

• t = Congested travel time
• t₀ = Free-flow travel time
• v = Volume on link
• c = Capacity of link
• α = 0.15 (standard value)
• β = 4.0 (standard value)

2. Traffic Studies and Data Collection

2.1 Traffic Volume Studies

2.2 Traffic Volume Characteristics

2.2.1 K-Factor and D-Factor

• K-Factor: Ratio of peak hour volume to AADT (K = PHV/AADT)
• K30: 30th highest hour (standard design hour = 0.08-0.12 of AADT)
• D-Factor: Directional distribution (peak direction/total peak hour volume)
• D = 0.50-0.70 (higher values indicate stronger directional flow)

2.2.2 Peak Hour Factor (PHF)

PHF = Hourly Volume / (Peak 15-min volume × 4)

• Range: 0.70-0.98
• Lower values indicate greater peaking within the hour
• Urban areas: 0.80-0.95
• Rural areas: 0.70-0.85

2.3 Origin-Destination Studies

2.4 Travel Time and Delay Studies

2.4.1 Floating Car Method

• Test vehicle travels with traffic stream
• Pass as many vehicles as pass the test vehicle
• Average travel time = Test run time
• Multiple runs required for statistical validity (minimum 3-4)

2.4.2 License Plate Method

• Record license plates and times at two locations
• Match plates to determine individual vehicle travel times
• Provides travel time distribution

2.5 Classified Volume Counts

3. Level of Service and Capacity Analysis

3.1 Level of Service (LOS) Definitions

3.2 Freeway Capacity

3.2.1 Basic Freeway Segment Capacity

• Capacity per lane: 2,200-2,400 pc/h/ln (passenger cars per hour per lane)
• Free-flow speed (FFS): 55-75 mph depending on design
• Density at capacity: 43-45 pc/mi/ln

3.2.2 Freeway Service Flow Rate

v_p = V / (PHF × N × f_HV × f_p)

3.2.3 Heavy Vehicle Adjustment

f_HV = 1 / [1 + P_T(E_T - 1) + P_R(E_R - 1)]

• P_T = Proportion of trucks and buses
• P_R = Proportion of RVs
• E_T = Passenger car equivalent for trucks
• E_R = Passenger car equivalent for RVs
• E values range from 1.5 to 6.0 depending on terrain and grade

3.3 Signalized Intersection Capacity

3.3.1 Saturation Flow Rate

s = s₀ × f_w × f_HV × f_g × f_p × f_bb × f_a × f_LU × f_RT × f_LT

• s₀ = Base saturation flow rate (1,900 pc/h/ln)
• f_w = Lane width adjustment
• f_HV = Heavy vehicle adjustment
• f_g = Grade adjustment
• f_p = Parking adjustment
• f_bb = Bus blockage adjustment
• f_a = Area type adjustment
• f_LU = Lane utilization adjustment
• f_RT = Right-turn adjustment
• f_LT = Left-turn adjustment

3.3.2 Capacity and Volume-to-Capacity Ratio

c = s × (g/C)

X = v/c

• c = Capacity (veh/h)
• s = Saturation flow rate (veh/h)
• g = Effective green time (sec)
• C = Cycle length (sec)
• X = Volume-to-capacity ratio (v/c ratio)
• X < 1.0="" for="" acceptable="">

3.3.3 Control Delay

d = d₁(PF) + d₂ + d₃

• d₁ = Uniform delay
• d₂ = Incremental delay (overflow delay)
• d₃ = Initial queue delay
• PF = Progression adjustment factor

3.4 Two-Lane Highway Capacity

• Capacity: 1,700 pc/h for both directions combined
• LOS based on: Average Travel Speed (ATS) and Percent Time Spent Following (PTSF)
• Class I: High-speed, through routes
• Class II: Access and scenic routes where speed less critical
• Class III: Serving developed areas with frequent access points

3.5 Pedestrian and Bicycle LOS

3.5.1 Pedestrian Walkway LOS

• Based on pedestrian space (sq ft per pedestrian)
• LOS A: > 60 sq ft/ped; free flow
• LOS E: 6-10 sq ft/ped; restricted flow
• LOS F: ≤ 6 sq ft/ped; breakdown

3.5.2 Bicycle Level of Traffic Stress (LTS)

• LTS 1: Suitable for children; protected facilities
• LTS 2: Suitable for most adults; low-speed mixed traffic
• LTS 3: Confident bicyclists; moderate-speed mixed traffic
• LTS 4: Strong and fearless; high-speed, high-volume traffic

4. Transportation System Planning

4.1 Planning Process

4.2 Metropolitan Planning Organization (MPO)

• Required for urbanized areas with population > 50,000
• Responsible for regional transportation planning
• Develops Long-Range Transportation Plan (LRTP): 20-year horizon minimum
• Develops Transportation Improvement Program (TIP): 4-year program of projects
• Must ensure fiscal constraint (funding availability)
• Public participation required

4.3 Key Federal Legislation

4.4 Transportation Planning Factors

• Economic vitality and global competitiveness
• Safety for all users
• Security of transportation system
• Accessibility and mobility for all people and freight
• Environmental protection and quality of life
• System integration and connectivity among modes
• Efficient system management and operation
• System preservation and maintenance
• Resiliency and reliability
• Tourism and recreation travel enhancement

4.5 Land Use and Transportation Integration

4.5.1 Trip Generation by Land Use

4.5.2 Smart Growth Principles

• Mixed land uses
• Compact building design
• Range of housing opportunities
• Walkable neighborhoods
• Distinctive communities with sense of place
• Preservation of open space and farmland
• Infill and redevelopment
• Multiple transportation choices
• Predictable development decisions
• Community and stakeholder collaboration

4.6 Performance Measures

5. Economic Analysis

5.1 Benefit-Cost Analysis

5.1.1 Key Formulas

B/C Ratio = PW(Benefits) / PW(Costs)

Net Present Value (NPV) = PW(Benefits) - PW(Costs)

PW = Σ[A_t / (1 + i)^t]

• PW = Present worth
• A_t = Cash flow in year t
• i = Discount rate (3%-7% for transportation projects)
• t = Year
• Accept project if B/C > 1.0 or NPV > 0

5.1.2 Analysis Period

• Highways: 20-30 years
• Pavements: 15-20 years
• Bridges: 50-75 years
• Traffic signals: 10-15 years
• Salvage value included if service life exceeds analysis period

5.2 Transportation Benefits

5.3 Value of Travel Time

• Personal travel: $15-25/hour (50% of wage rate approximation)
• Commercial/freight: $25-50/hour (varies by vehicle type)
• Varies by trip purpose (work vs. recreation)
• In-vehicle vs. out-of-vehicle time (waiting time valued 2-3 times higher)

5.4 Crash Costs by Severity

5.5 Life Cycle Cost Analysis (LCCA)

EUAC = (P × CRF) + A

CRF = [i(1 + i)ⁿ] / [(1 + i)ⁿ - 1]

• EUAC = Equivalent uniform annual cost
• P = Initial cost
• CRF = Capital recovery factor
• A = Annual recurring costs
• i = Interest rate
• n = Analysis period (years)

5.5.1 LCCA Components

• Initial construction cost
• Maintenance and rehabilitation costs over life
• User costs (delays during construction/maintenance)
• Salvage/residual value at end of analysis period
• All costs converted to present worth or EUAC for comparison

5.6 Economic Impact Analysis

5.6.1 Multiplier Effects

• Direct impacts: Jobs and spending from project construction
• Indirect impacts: Supply chain effects in supporting industries
• Induced impacts: Household spending from project-generated income
• Multiplier values: 1.5-2.5 for transportation infrastructure

6. Multimodal Transportation

6.1 Transit Planning

6.1.1 Transit Service Types

6.1.2 Transit Performance Measures

6.1.3 Transit Capacity

Capacity = (3600 / Headway) × Load Factor × Vehicle Capacity

• Headway in seconds
• Load factor: 0.85 for seated capacity; 1.0-1.5 for crush load
• Minimum headway: 90-120 seconds (surface); 90 seconds (grade-separated)

6.2 Pedestrian Planning

6.2.1 Pedestrian Design Standards

• Minimum sidewalk width: 5 ft (4 ft in constrained areas)
• Effective walkway width: Exclude 1.5 ft shy distance from curb/wall
• Crosswalk width: 6 ft minimum; 10 ft preferred
• Curb ramp slope: Maximum 1:12 (8.33%)
• Detectable warning surface required at curb ramps

6.2.2 Pedestrian Signal Timing

Walk Interval = 7 seconds (minimum)

Pedestrian Clearance = L / (3.5 ft/sec)

• L = Crosswalk length (ft)
• Walking speed: 3.5 ft/sec (standard); 3.0 ft/sec (older pedestrians)
• Flashing Don't Walk = Pedestrian clearance interval

6.3 Bicycle Planning

6.3.1 Bicycle Facility Types

6.3.2 Bicycle Design Speed and Clearances

• Design speed: 20 mph (recreational paths); 30 mph (experienced cyclists)
• Minimum width: 4 ft (bike lane); 5 ft preferred
• Operating space: 4 ft wide × 7 ft high
• Passing clearance: 2 ft minimum between cyclists
• Door zone: 3-5 ft from parked cars

6.4 Freight Planning

6.4.1 Truck Classifications

• Light Trucks: 2-axle, 4-tire (delivery vans, pickups)
• Medium Trucks: 2-axle, 6-tire single unit
• Heavy Trucks: 3+ axle single unit; tractor-trailers
• Design vehicle: WB-67 (wheelbase 67 ft) for arterials; WB-50 for local roads

6.4.2 Truck Route Criteria

• Pavement structural capacity for truck loads
• Geometric design: Turning radii, vertical clearance (14 ft minimum)
• Bridge load limits (posted weight restrictions)
• Access to freight generators (warehouses, industrial areas)
• Minimize truck traffic through residential areas

6.5 Intermodal Connectivity

6.5.1 Park-and-Ride Facilities

• Location: Major corridors, transit stations, freeway interchanges
• Parking demand: Peak parking accumulation at AM period
• Design: Access/egress, bus bays, lighting, security, wayfinding

6.5.2 Transfer Facilities

• Transit centers: Multiple routes; timed transfers; passenger amenities
• Intermodal terminals: Integration of bus, rail, air, taxi, rideshare
• Design considerations: Minimized transfer distances and wait times

7. Environmental and Social Considerations

7.1 NEPA Process

7.1.1 EIS Components

• Purpose and need statement
• Alternatives analysis (including no-build)
• Affected environment description
• Environmental consequences assessment
• Mitigation measures
• Public and agency coordination
• Record of Decision (ROD) documenting final selection

7.2 Air Quality Analysis

7.2.1 Transportation Conformity

• Required in nonattainment and maintenance areas
• TIP and LRTP must conform to State Implementation Plan (SIP)
• Projects cannot cause new violations or worsen existing violations
• Emissions budgets from approved SIP must not be exceeded

7.2.2 Mobile Source Emissions

7.3 Noise Impact Analysis

7.3.1 Noise Metrics

• L_eq: Equivalent sound level (average over time period)
• L₁₀: Sound level exceeded 10% of time (peak)
• L_dn: Day-night average (10 dB penalty for nighttime noise)
• Highway noise: 67 dB(A) approach (exterior) for residences
• Substantial increase: 10-15 dB(A) over existing conditions

7.3.2 Noise Abatement Measures

• Noise barriers: Earth berms or walls; minimum 5 dB reduction for feasibility
• Quiet pavement: Porous asphalt; 3-5 dB reduction
• Traffic management: Speed reduction, truck restrictions
• Land use planning: Setbacks, buffers, compatible uses

7.4 Stormwater Management

7.4.1 NPDES Requirements

• MS4 permits for municipal stormwater systems
• Construction stormwater permits for sites > 1 acre
• Six minimum control measures: Education, public participation, illicit discharge, construction, post-construction, pollution prevention

7.4.2 Best Management Practices (BMPs)

• Retention basins: Permanent pool; pollutant settling and uptake
• Detention basins: Temporary storage; peak flow reduction
• Infiltration systems: Bioswales, rain gardens, permeable pavement
• Water quality treatment: 80% removal of total suspended solids (TSS)

7.5 Environmental Justice

7.5.1 Key Principles

• Identify minority and low-income populations
• Assess disproportionately high and adverse effects
• Ensure benefits and burdens fairly distributed
• Provide meaningful public involvement opportunities
• Language access for limited English proficiency (LEP) populations

7.5.2 Protected Populations

• Minority populations (racial/ethnic minorities)
• Low-income populations (below poverty threshold)
• Children and elderly
• Persons with disabilities
• Analysis at census block group or tract level

7.6 Section 4(f) and Section 6(f)

7.6.1 Section 4(f) Properties

• Public parks, recreation areas, wildlife refuges
• Historic sites (listed or eligible for National Register)
• Use only if no prudent and feasible alternative exists
• Minimize harm through all possible planning
• De minimis impact: Minimal impact with mitigation; no adverse effect

7.6.2 Section 6(f)

• Protects properties acquired or developed with Land and Water Conservation Fund (LWCF)
• Conversion requires replacement property of equal value and usefulness
• National Park Service approval required

7.7 Cultural Resources

7.7.1 Section 106 Review

• National Historic Preservation Act compliance
• Identify historic properties in Area of Potential Effects (APE)
• Assess effects: No effect, no adverse effect, adverse effect
• State Historic Preservation Officer (SHPO) consultation
• Mitigation: Avoidance, minimization, documentation

8. Transportation Safety

8.1 Crash Analysis Methods

8.1.1 Crash Rate Calculations

Intersection Crash Rate = (C × 1,000,000) / (365 × ADT × N)

Roadway Segment Crash Rate = (C × 100,000,000) / (365 × ADT × L × N)

• C = Number of crashes
• ADT = Average daily traffic
• L = Length in miles
• N = Number of years
• Results in crashes per million entering vehicles (MEV) or per 100 million vehicle-miles (VMT)

8.1.2 Crash Severity Index

• K (Fatal): 5 points
• A (Incapacitating): 3 points
• B (Non-incapacitating): 2 points
• C (Possible injury): 1 point
• O (Property damage only): 0 points
• Severity index = Σ(crashes × severity points) / total crashes

8.2 Highway Safety Manual (HSM)

8.2.1 Crash Prediction Methods

N_predicted = N_spf × CMF₁ × CMF₂ × ... × CMF_n × C

• N_spf = Safety performance function (base crash frequency)
• CMF = Crash modification factor (geometric and traffic control features)
• C = Calibration factor (local conditions)

8.2.2 Empirical Bayes Method

N_expected = w × N_predicted + (1 - w) × N_observed

• Combines predicted and observed crashes
• w = weighting factor based on overdispersion parameter
• Accounts for regression-to-mean bias
• Used to identify sites for safety improvements

8.3 Crash Modification Factors (CMFs)

8.4 Road Safety Audits (RSA)

8.4.1 RSA Process

• Formal safety review by independent multidisciplinary team
• Applicable at all project stages (planning through operation)
• Site visits and documentation review
• Identification of safety concerns for all users
• Report with findings and potential countermeasures

8.4.2 Common RSA Findings

• Inadequate sight distance
• Confusing or missing signs and markings
• Conflicts with pedestrians or bicycles
• Roadside hazards (fixed objects, steep slopes)
• Intersection geometric deficiencies
• Inadequate drainage or lighting

8.5 Strategic Highway Safety Plan (SHSP)

• Statewide coordinated safety plan
• Data-driven process to identify emphasis areas
• Performance targets (fatality and serious injury reduction)
• Strategies addressing four "E's": Engineering, Enforcement, Education, Emergency response
• Required for Highway Safety Improvement Program (HSIP) funding

8.6 Work Zone Safety

8.6.1 Temporary Traffic Control

• Manual on Uniform Traffic Control Devices (MUTCD) Part 6 requirements
• Work zone elements: Advance warning, transition, buffer, activity, termination areas
• Taper length = WS/2 (W = width shifted in ft; S = speed in mph)
• Minimum taper length: 100 ft per lane (urban); 200 ft per lane (rural)

8.6.2 Work Zone Crash Rates

• Work zone crash rates 2-3 times higher than non-work zone
• Rear-end crashes most common work zone crash type
• Positive protection devices: Temporary concrete barriers, truck-mounted attenuators