CHAPTER 8

THE THEORY OF URBAN PASSENGER TRANSPORT MODES

GUIDELINES FORPASSENGER TRANSPORT IN SOUTH AFRICA

A MULTI MODAL ANALYSIS

8.1 Introduction

• Transport and transport systems are very complex and difficult analyse.

• No rational policy and planning of urban transport can be achieved without a thorough understanding of the characteristics of different modes.

8.2 Transportation System Evolution in a Model Urban Area

• Transport system must be understood and analyze without factors that would influence you, like:– investment, – pricing, and– regulatory policies favouring one mode

• A conceptual analysis based on a model of an urban area of changing population and size will therefore be used.

8.2 Transportation System Evolution in a Model Urban Area cont’

• The Model:– represents a residential area that grows from a small

settlement to a large metropolis– Requirements for transport change through

• from low volume, dispersed travel to • high volume, heavily concentrated travel along a number of

major arterials.

– Entire range of requirements is observed and the optimal sequence of transport modes through the entire spectrum of capacities and performance levels is defined in a systematic way.

• The analysis is divided into four growth periods, which correspond approximately to 1. small settlements, [up to 100,000 –population

size]2. towns, [100,000 to 500,000]3. medium-size and , [500,000 to 2 million]4. large cities [over 2 million]

8.2 Transportation System Evolution in a Model Urban Area cont’

8.3. A Description of Typical Rights-of-way (R/W)

8.3.1 Right-of-way: Category A• Ultimate in systems, – carrying capacity and – safety,

• Exclusive right-of-way is given along its total length with no pedestrian or vehicle conflict.

• It may be either elevated, at surface level, or underground, depending on availability of space and land values.

8.3. A Description of Typical Rights-of-way (R/W) cont’

8.3.2 Right-of-way: Category B• Longitudinally separating the right-of-way from other

traffic by devices such as kerbs, barriers and fences • Result –

– capacity of the system is dramatically increased and – pedestrian vehicle conflict limited to intersections where it can

be minimised by orderly control of using traffic signal systems. • Far higher average and overall operating speeds can be

maintained and a clear advantage in terms of travel time is achieved, especially in congested city town streets.

8.3.3 Right-of-way: Category C• the right-of-way shared with other users. • The operational safety of the system is entirely the

responsibility of the driver; • consequently vehicles must have braking

characteristics similar to those of ordinary road vehicles.

• Nevertheless, some degree of priority can be given at traffic signal controlled intersections to give preference over normal vehicular traffic.

8.3. A Description of Typical Rights-of-way (R/W) cont’

8.4 Transportation System Evolution

We’ll follow the growth of the hypothetical settlement as it grows through the following stages:

1. small settlement2. town3. medium - size city4. large city

8.4 Transportation System Evolution cont’

8.4.1 Small settlement - walking and private carsStep1: WalkingStep 2: Private CarsStep 3: Common Carriers

(Taxis)

• Private cars and taxis comprise an ideal transportation system for small, low-density settlements

8.4.2 Towns: arterials and public transport

Step 4 - Wider Roads and Streets

(multilane roads and streets)• The capacity of the transport

system must be increased. Two measures are most logical:

1. widening of the paths, and 2. introduction of larger cabins (busses).

8.4.2 Towns: arterials and public transport cont’

Construction of higher-capacity ways (paths) brings:Advantages: – Higher levels of service. (L/S)– Lower unit transportation costs.– Stimulus to economic growth (result of the preceding

two).

Disadvantages– High investment requirements.– Negative environmental impact of wide paths and large

cabin storage facilities.

Step 5: Larger Vehicles and Formal Public Transport

• Capacity increase through introduction of large cabins can be achieved only with common carrier (public transport) service.– Midibuses - For low passenger volumes, medium-

capacity cabins that stop wherever passengers want – the bus - As the volume increases it becomes

necessary to introduce large-capacity cabins

8.4.2 Towns: arterials and public transport cont’

• Changing public transport from small to large:• Large public transport vehicles differ to

smaller ones by:– travel along fixed routes, – stop at predetermined locations, and – serve large numbers of persons– Schedules are fixed and – It has regular frequencies– Fares are somewhat lower

8.4.2 Towns: arterials and public transport cont’

(L/S = Level of service)

(R/W = Right of way)

• Introduction of formal public transport service results in the following changes:

Advantages:– Lower-cost transportation becomes available to all

persons in the area served.– Simple and conveniently scheduled service is

provided throughout the public transport network.– Increased street capacity: higher L/S for all vehicles.– Less congestion and its negative impacts.

8.4.2 Towns: arterials and public transport cont’

Disadvantage:• Since it is difficult to charge small-cabin drivers

the full cost (including social) of their travel, public transport must often be subsidised to attract its potential passengers.

8.4.2 Towns: arterials and public transport cont’

• Replacement of medium by large public transport vehicles or units (TUs) results in:

Advantages:– Higher transporting capacity.– Lower cost per unit capacity, mostly due to higher

labour productivity.– Greater riding comfort.

Disadvantage:– Lower service frequency for given demand.

8.4.2 Towns: arterials and public transport cont’

Conclusion:(1) optimal vehicle size increases with passenger

volume and(2) service with adjustable routing and schedules

should be replaced (or complemented) by fixed routes and schedules as passenger volumes increase.

• (Learners are reminded of the conclusion in chapter 6 where it was stated that both the formal and informal sectors should co-exist where necessary)

8.4.2 Towns: arterials and public transport cont’

8.4.3 Medium-size cities: technology mode separation and guided

• Step 6: Separation of public transport on its own right- of-way [from category C to B]– create separate rights-of-way for different types of

cabins, so that a smooth flow, with no friction from other vehicles, pedestrians, and so on, is obtained.

– Longitudinal separation (R/W category B) is the 1step for the reduction of interferences, because conflicts at intersections of paths can be regulated through traffic control devices

– Public modes should be given separate rights-of-way first because the carry 5-50 times more people

8.4.3 Medium-size cities: technology mode separation and guided cont’

Longitudinal separation of public transport vehicles (R/W category B) results in:

Advantages:• Higher level of service and system performance.• Stronger system image and identity.• Higher passenger attraction (consequence of

the above two).• Lower unit operating cost.

8.4.3 Medium-size cities: technology mode separation and guided cont’

Advantages cont’:• Stronger impact on land use and urban form

due to permanence.• Changed traffic conditions, depending on

whether the public transport R/W is outside or within existing streets (e.g., curbed median).

8.4.3 Medium-size cities: technology mode separation and guided cont’

Disadvantage:• Changed traffic conditions, depending on

whether the public transport R/W is outside or within existing streets (e.g., curbed median).

• Additional land required.• Substantial investment and construction

required.

8.4.3 Medium-size cities: technology mode separation and guided cont’

Step 7 - Introduction of Guided Public Transport• Guided modes, compared with steered public transport

modes, differ in the following:• Advantages:

– Higher capacity and productivity due to operation of trains.– Lower operating cost per unit of offered capacity.– Electric traction possible + Greater reliability and safety (fail-

safe operation).– Narrower R/W.– Operation in tunnels, on viaducts, and in park areas possible

without significant environmental damage.

8.4.3 Medium-size cities: technology mode separation and guided cont’

• Disadvantage:– Less compatible with other traffic in street

operation.– Limited to the guideway network only, therefore

uneconomical for extensive routing in low-density areas.

– Lower operational flexibility (rerouting, detours, etc.).

– Requires higher investment.

8.4.3 Medium-size cities: technology mode separation and guided cont’

8.4.4 Large cities: addition of fully controlled ways

8.4.4 Large cities: addition of fully controlled ways cont’

Step 8: Construction of freeways• heavy travel volumes in many corridors and • large spatial size, • requires higher performance transportation• Solution: Fully Controlled Rights-of-way (that

is category A) for major routes of both private and public modes.– speed, capacity, and reliability for >2mil people

Step 9 - Fully Controlled Right of Way for Public Transport (rapid public transport)

• Category A, compared with Category B R/W, gives public transport modes:

Advantages:• Higher performance (capacity-long trains,

speed, reliability, etc.).• Higher L/S.• Lower operating costs per unit capacity.

8.4.4 Large cities: addition of fully controlled ways cont’

Advantages cont’:• Stronger image and identity.• Higher passenger attraction (result of the

preceding three).• Stronger land use impacts.• Possibility of automation.

8.4.4 Large cities: addition of fully controlled ways cont’

• Disadvantage:• Need for grade separation of the entire RIW,

resulting in• High investment needs.• Disruptions of the corridor during the

construction.• Less extensive network (result of the

preceding three).

8.4.4 Large cities: addition of fully controlled ways cont’

• Step 10: Full Automation• There is only one additional major improvement

that can be made: – full automation of train (trains without crews). – technology of line-haul public transport > ultimate step

of development that can be practically achieved.• Full automation requires two features:

1. R/W category A, and 2. guided technology.

• Rail systems are best candidates

8.4.4 Large cities: addition of fully controlled ways cont’

8.5 Review of Modal Features

• There is a strong interdependence between the volume of travel and the characteristics of modes optimal for a given application.

• Serious transportation problems in many cities have been created, for example, – when extensive freeway networks were built to

accommodate and stimulate motor car travel, while public transport consists only of buses in mixed traffic.

8.5 Review of Modal Features cont’

• Step 1, walking, remains essential for cities of all sizes (actually, it is often more important in large cities than in small settlements), yet many cities have neglected it while they worked on accommodating motorised traffic through steps 2, 4, and 8.

8.6 Higher performance modes

• The evolutionary development process shows that with increasing density of travel, each new modal feature results in:– Higher system performance, including capacity,

speed, and service quality.– Greater passenger attraction (consequence of the

preceding result).– Higher initial investment.– Lower operating cost per unit capacity.

8.7 Conclusion

• As the town expanded and grew, not only were new modes necessary, but new methods of operation and new infrastructure was required to operate and accommodate them effectively.

• This chapter also noted that there is no ‘exact’ economic boundary between modes and that higher-performance modes can be introduced at an earlier stage because of their higher passenger attraction.