Urban streets

Raghupathi

Outline

1. Need for the study

2. Objectives

3. Classification

4. Operational performance measures

5. Congestion management

6. Case study: pune

Urban Streets

• NEED FOR THE STUDY

• Study, understand, resolve

Shifting of people from

rural

to urban areas

Increasing urban

population

Increasing vehicular

population on urban streets,

Congestion in urban areas

• Objectives

• To develop efficient street transportation

• To serve effectively various land use in an urban area

• Ensure community development

• Classification of urban streets

Functional based

• Principal Arterial streets

• Minor Arterial streets

• Collector street

• Local roads

Design based

• High speed

• Suburban

• Intermediate

• Urban

Combination of functional and design

based

• Class I

• Class II

• Class III

• Class IV

Function based classification of urban streets

• According to the character of service they are intended to provide.

• Principal arterial system

• Arterial streets are basically meant to carry longer and through traffic.

• To be connected with principal traffic generations, important rural highways

• Should carry the major portion of trips entering and leaving the urban area

• Minor Arterial streets

• Should interconnect with and augment the urban principal arterial system

• Provide service to trips of moderate length

• Level of travel mobility is lower than principal arterials.

• Carry local bus routes and provide intra-community continuity.

• The spacing of minor arterial streets

• may vary from half to one km

in the central business district.

• 4 to 5 km in the suburban fringes

• not more than 2 km in fully

developed areas.

• Collector streets

Includes all distributer and collector streets.

Serving between major arterials and local streets to connect adjacent

neighborhood

Placed approximately at half miles intervals

• Local Street

Meant for direct access to residential commercial, industrial or other

abutting property

Land access is very high but mobility is very low for local streets.

Design based Classification

• High speed streets

With very low driveway or access point density.

Separate right turn lanes

Signals are infrequent and spaced at long distances

No parking is permitted on street.

speed limit on these roads is 75 to 90 kmph.

• Sub-urban streets

With a low driveway/access-point density

Comparatively higher density of roadside development

Speed limit on these roads is 65 to 75 kmph

• Intermediate design streets

urban streets with moderate driveway/access point density.

Separate or continuous right turn lanes

It has about two to six signals per Km.

speed limit on these roads is 50 to 60 Kmph.

• Urban streets

With high driveway/access point density.

Usually provided with road side parking.

Signal density is about four to eight per Km.

Speed limit is 40 to 55 Kmph.

Combination of functional and design based

Specifications of street classes

Combined classification of urban streets

Operational performance measures

To quantify how well the ’system’ or ’facility is working

1. Assessing the existing condition

2. Evaluating alternative improvements

3. Quantifying associated cost and benefits

4. Communicating results to both technical and non technical people

Arterial LOS

• Mainly based on average travel speed for the considered segment

• Avg travel speed is computed from the running times and the control delay

• Delays of initial deceleration

• move-up time in the queue

• Stops and re-acceleration

• Factors influencing the performance of urban streets

Number of signals per kilometer

Intersection control delay

o Inappropriate signal timing

o poor progression

o Increasing traffic flow can degrade the LOS substantially

HCM Method of performance measurement

• Aim to compute ’average travel speed’ of arterial to measure the LOS

• Involves seven steps

1. Establish arterial to be considered

2. Determine arterial class by free flow speed

3. Define arterial section

4. Compute running time

5. Compute intersection approach delay

6. Compute average travel speed

7. Estimate the LOS.

Step 1: Establish arterial to be considered

Define arterial segment or entire arterial whose LOS is to be determined.

Established by arterial class, its flow characteristics and signal density.

Step 2: Determine arterial class by free flow speed

“Free flow speed is the speed on the arterial which most of the drivers

choose if they had green indication and they are alone in the direction of

movement”

An arterial can be classified on the basis of its free flow speed

Range and typical values of FFS for different arterial classes

Step 3: Define arterial section

It is required to be more specific about the particular section

• Mid block

• Intersection

Step 4: Arterial running time

Signalized intersections

generally considered

Total time that a vehicle spends

Running time

Segment

lengthFree flow

speed.

Control delay at signalized

intersections.

• Step 5: Intersection Approach Delay

Delays of initial deceleration

move-up time in the queue

Stops and re-acceleration

• This can be related to intersection stopped delay

D =1.3*d

where, D = intersection approach delay (sec/veh), and

d = intersection stopped delay (sec/veh).

• intersection stopped delay is determined from field

• Stopped Delays

Stopped vehicles on intersection are counted for intervals of 10 to

20 seconds.

Maximum extent of queue length on intersection approach during

the study period must

be observed in advance

Count intervals are set at 10, 15, or 20 seconds stopped vehicles

within the queuing area observed and recorded at each interval.

Discharge volumes are separately counted for the study period.

Step 6: Average travel speed

𝑉𝑎𝑣𝑔 =3600𝐿

𝑇𝑟 ∗ 𝐿 + 𝐶

where,

vavg = arterial or segmental average travel speed (Kmph),

L = arterial or segmental length (Km),

Tr = total of the running time per kilometer on all segments in the

arterial or section (seconds),

D = total of the approach delay at all intersections within the defined

arterial (seconds)

Step 7: Estimate the LOS

• Based on average travel speed LOS can be determined

Urban Street LOS by Class and Average Travel Speed

Numerical 1• In an intersection the following data was observed for stopping times

for vehicles as tabulated. Calculate intersection approach delay for the

given data set. Total exiting vehicles: 100. If free flow speed of 65 kmph

and average running time of vehicles is 145 sec/km determine LOS for

this arterial.

Solution:

• Total of stopped-vehicle counts for study sample is:

= 33 + 34 + 31 + 24 = 122 veh.

• Each of the vehicle interval is 15 seconds. Aggregate delay for the 10

minutes study period is

= 122 × 15 sec =1830 veh-sec.

• Average stopped delay per vehicle for study period of 10 minutes is,

1830/100 =18.3 sec per vehicle.

i.e. d=18.3 sec per vehicle.

• Intersection approach (or control) delay D

D = 1.3 × d = 1.3 × 18.3 = 23.79 sec/veh

• Free flow speed is 65 kmph

• By using above table, we can classify this as Arterial Class II,

• Average travel speed….?

• Deleay D=23.79sec/veh.

𝑉𝑎𝑣𝑔 =3600𝐿

𝑇𝑟 ∗ 𝐿 + 𝐶

= (3600 × 1) / (145 + 23.79)

= 21.32 km/hr

• Average travel speed is 21.32 kmph

• Now LOS from above Table ’E’

Congestion Management

• Demand on a facility exceeds the capacity Congestion takes place.

• Delay is in excess upon normal may vary by

• Type of transport facility

• travel mode

• geographical location

• time of day.

Congestion management

find out the root cause of congestion

finding out the

remedies

updating the signalization

• Managing surface street congestion

Managing surface street congestion

1. Signal based

Metering plans Reasonably

shorter cycle lengths

2. Non-signal based

Two way turn lanes

Reversible lanes

Kerbparking

prohibition

Lane marking

1. Signal based remedies

Metering plans

limit the volumes arriving at critical locations

Does not explicitly minimize delays and stops but manages queue

formation.

Three types of metering strategies

o Internal metering

o External metering

o Release metering

o Internal metering

• Deals with upstream control by creating moving storage situation

• Manages congestion by limiting turn-in flows from cross streets

o External metering

• Control of major access points so as to limit inflow rates.

• Example

River crossing,

downtown surrounded by water from three sides,

a system that receives limited no. of arterials etc.

o Release metering

Controlling the release of vehicles from stored locations

Parking, garages etc which are stored are stored off-street

This type of metering can be used in shopping centers, mega center, etc.

Shorter cycle length

• Higher cycle length – Increase in que length – Increase in blockage –

decrease in system capacity.

• Especially when short link lengths are involved.

• Length of downstream space > queue length to store the vehicles.

Length of downstream space > queue length to store the vehicles

𝑉𝑖𝐶

3600∗ 𝐷 ≤ L

Where,

• 𝑉𝑖 is critical lane flow in veh/hr

• C = cycle length in sec

• D= storage space required for each vehicle in m

• L= available downstream space in m

Hence Short Cycle length

𝐶 ≤ 3600

𝑉𝑖

𝐿

𝐷

• Only for high flows, maximum f > 800 veh per hour per lane and short blocks

Numerical 2

Flow on an critical lane is 300 veh/h, cycle time is 80 seconds, suppose

storage space required per lane vehicle is 6m as an average and space

available on downstream is 30 m, find whether the space is sufficient and

comment on the result and suggest some remedy if required.

Solution:

Given: Vi = 300 veh/h, C = 80 sec, and L = 30 m.

Vehicles discharged by a critical lane per cycle

= 𝑉𝑖𝐶

3600

= 300 * 80/3600 = 60/9

=6.6 veh/cycle

• space required for storing these vehicles for cycle time is,

= 6.6 *D = 6.6 * 6, = 39.6 m ≈ 40 m > 30m

• So length is inadequate.

• Remedy: Change cycle time: Let the new cycle time 40 sec

• Space required will be : 20 m < 30m

• So it is feasible to reduce the cycle length to manage the congestion.

2. Non-signal based remedies

Two way turn lanes

Dedicated lane for two

way turns

vehicle leaving arterial in two steps vehicle entering arterial in two steps

Reversible lane

• Can matching lane availability to the peak demand

High occupancy vehicle (HOV) lanes

• Designed to help move more people through congested areas

• HOV lanes are reserved for any of the passenger vehicles carrying at least

two people.

• Motorcycle, Car

• Commercial truck less than 6.5 meters long

• Minivan, Taxi or limousine

• special green license plate.

• Bus of any type can use HOV to be reliable

• Emergency vehicles are permitted

Kerb Parking Prohibition

Lane marking

• Lane marks will guide vehicles

in particular lane and will

reduce congestion.

High Occupancy Vehicle Lane

HOV lane

Downtown 2-Way Street congestion management(nacto.org/publication/urban-street-design-guide/streets)

Downtown Thoroughfare congestion management

Case study: Pune

Objectives

• To develop street hierarchy and

establish design parameters

• Design people friendly streets

• Integrating measures to promote

non motorized vehicles and

public transport.

• To formulate design guidelines and

specifications

Pune road network

Pune streets are categorized as follows

• Mobility corridors – Arterial streets

• Collector/ Distributor/Feeder corridor – Sub Arterial streets

• Neighborhood corridors – Local streets

• Special streets – Pedestrian, High stretches, food streets etc.

Current condition of urban roads in pune

Essential goals • Carriage way – MV

• Foot path, Cycle track

• Parking – 2W, 3W and Car

• Goods carriage and BRTS lanes

Mobility and Accessibility

• Dead width for footpaths

• Traffic calming measures

• Refuse Islands

• Street furniture

Safety and comfort

• Trees and plantation

• Public toilets

• Garbage cans

• Rain water harvesting

Ecology and environment

• Traffic calming should provide all local roads less than 21m

Refuse Island

Access requirements of urban roads