Generalized Needs Assessment Scenarios for Transportation Infrastructure!

Ashish Samdariya, Qiang Bai, Anwaar Ahmed, Eleni Bardaka, and Samuel Labi!

§ Transportation planners monitor trends in transportation system supply and demand !

§ Purpose of monitoring is to predict reliably the direction and magnitude of future gaps !

§ Such information needed for taking appropriate palliatives to mitigate any expected gaps between demand and supply. !

§ Need for optimal and phased supply schedule for the entire new or remaining life of any infrastructure!

§ Purpose is to minimize life-cycle cost (underutilized capacity and user cost) over the life of the infrastructure.!

MOTIVATION!

CATEGORIZING SYSTEM NEEDS !

DEMAND AND SUPPLY SCENARIOS!

CONCLUSIONS!§  Paper provides a generalized quantitative assessment of supply

and demand gaps!§  Presents mathematical derivations for!

!- cases where demand and continuous and supply is discrete; - cases where both supply and demand are continuous. !

§  Case study shows the development of an optimal capacity expansion schedule for Beijing Capital International Airport.!! !- Compared optimal and actual supply schedules !! !- Found that actual capacity-supply schedule not very !!! responsive to the growing demand in the years 25-35!! ! - Thus, significant user delay was encountered in that period.!

§  Optimal solution is sensitive to the relative weights of agency and user costs.!

CASE STUDY!§ The Beijing Capital International Airport (BCIA) !

§ World’s 2nd and 8th busiest airport in terms of passenger traffic and total aircraft movement.!

§ Passenger traffic increased from 100 to 130 in past 10 years. !§ Capacity expansions were carried out to meet passenger traffic

demand, which has been growing exponentially. Current BCIA attributes are as follows:!

§ In 2009 and 2011, passenger delays were 30-60 minutes per passenger at BCIA!

§ when the capacity exceeds the demand, delay will be negligible but when demand exceeds capacity, passengers will face larger time delays. !

§ The resulting optimal schedule for capacity provision over the 35 year analysis period is presented below:!Need!

Growing Need!

Gradually Decreasing Supply!

Gradually Increasing Demand!

Sudden Need!

Sudden Decrease in Supply!

Sudden Demand or Sudden Increase in

Demand!

Planned!

Unplanned!

!

Initial System Capacity Projected Demand

(Linear) Time

Demand, Supply

!

!

ΔT!

ΔS!

!

ΔT!

ΔS!

!

DETERMINING OPTIMAL SCHEDULE OF CAPACITY PROVISION!

NPVAgency = C0 (S0 )+C(ΔS1)(1+ r)T1

+ C(ΔS2 )(1+ r)T2

++ C(ΔSm )(1+ r)Tm

NPVUser = UC(St,Dt, t)T1*

T1

∫ dt + UC(St,Dt, t)T2*

T2

∫ dt + UC(St,Dt, t)Tm*

N

∫ dt

Min Z = wagencyNPVAgency +wuserNPVUsert-- time in years; N-- analysis period; r-- effective annual interest rate; !Ti-- the time (year) of the ith expansion; T*

i -- the time (year) of the ith time that the demand catches up with the supply; m-- the total number of expansions in the analysis period; !D(t)--demand function; S(t)--Supply function;!C(ΔS)--agency cost function, a function of additional supply; S0 -- the initial supply; !C(S0) --Initial construction agency cost; !UC(St, Dt, t,) --user cost function, a function of time t and the demand and the supply at time t; wagency and wuser are the weights of agency cost and user cost !

BCIA Terminal! Area! Design Capacity!Terminal 1! 60,000 m2! 9,000,000 PAX/yr!Terminal 2! 336,000 m2 ! 26,500,000 PAX/yr!Terminal 3! 986,000 m2 ! 60,000,000 PAX/yr!

0 10 20 30 40 50 60 70 80

0 10 20 30 40 50 60 70 80

0 5 10 15 20 25 30 35 40

Cap

acity

(in

M)

Pass

enge

r Tra

ffic

(in M

)

Year (1975-2010)

Demand (D) "Capacity (C)"

Need Type! Examples!Growing Need! Deterioration of transit service quality due to

neglect and lack of maintenance and aging of the system components !

Growing demand ! Social and economic changes gradually translate into the need to provide a new transportation system !

Gradually Decreasing Supply!

Service provided by the transportation system gradually erodes over time!

Sudden Demand! Requirement of providing a structural element as part of an ongoing design !

Sudden Surge in Demand!

Where natural or manmade events overwhelm the existing system !

Sudden Decrease in Supply!

Sudden failure of a bridge!

Growing populations, demographic shifts, and expanding economies and other development sectors translate constantly into the need for new or expansions in highways and streets, urban commuter rail, water ports, airports, pipelines, and other transportation infrastructure.!

!

Demand, Supply

Initial System Capacity

Projected Demand

(Linear)

Time (i)

Initial System Capacity

Projected Demand

(Linear)

Time (ii)

Demand, Supply

!

Demand, Supply

Initial System Capacity

Projected Demand

(Linear)

Time (i)

Initial System Capacity

Projected Demand

(Linear)

Time (ii)

Demand, Supply

!

Demand, Supply

Capacity

!

Time (c)

Demand

t*#

Demand, Supply

Capacity

!

Time

(d)

Demand

t*#

t**#

!

Demand, Supply

Capacity

!

Time (e) t*#

Demand

Demand, Supply

Capacity

!

Time (f) t*#

t**#

Demand