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TRANSPORTATION PLANNING

Transportation planning consists of t"ose acti*ities t"at collect information on t"e

performance of t"e e/isting transportation system; forecast future performance le*els gi*en

e/pected c"anges to 0ey factors suc" as land use, price of fuel, and gro#t" in employment; and

identify solutions to e/pected pro1lems in system performance.

Bs!" E#e$ents o% Trns&ortt!on P#nn!n'

Transportation planning is a process t"at consists of #ell&defined tas0s t"at must 1e

accomplis"ed 1efore t"e final set of information is presented to t"ose #"o must decide #"ic"

course of action is 1est for a region or community. Fig. 2 1elo# presents a planning frame#or0 t"at

s"o#s 1asic tas0s as #ell as t"eir interrelations"ip.

(!') * Bs!" e#e$ents o% trns&ortt!on nn!n'

As s"o#n in t"e Fig. 2 a1o*e, transportation planning is primarily a process of producing

information t"at can 1e used 1y decision ma0ers to 1etter understand t"e conse3uences of different

Monitor 'ystemPerformance

De*elop and Analy4eAlternati*es

Identify Deficiencies

and pportunities

$oals and

15ecti*es

Facility

In*entory

'ocio&economic

and +and 6seData1ase

E*aluateAlternati*es

Implement Plan

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courses of action. T"e tas0s t"at are part of identifying and assessing t"ese conse3uences include

t"e follo#ing7

In+entor, o% ("!#!t!es

Transportation engineers and planners must 0no# #"at t"e transportation net#or0 consistsof and t"e condition and performance of t"ese facilities. In a state or ur1an area, muc" of t"e

transportation in*estment is aimed at upgrading t"e p"ysical onditionof a facility (e.g., repa*ing a

road or 1uilding a ne# 1ridge) or impro*ing its !erfor"ane(e.g., 1uilding a ne# road to ser*e

e/isting demand).

Transportation agencies are e/pected to "a*e a *ery e/tensi*e in*entory of road system in

t"eir 5urisdiction including num1er of lanes, type of pa*ement, t"e last time t"e pa*ement #as

replaced, t"e capacity of t"e road, accident record, etc. Transit agencies are also e/pected to "a*e

an in*entory of t"e different assets t"at constitute a transit system (e.g., 1uses, stations, s"elters, rail

cars, etc.).

Co##e"t n- .!nt!n So"!oe"ono$!" n- Ln- Use Dt

+and use maps and ot"er sources can 1e used to collect information suc" as t"e num1er of

trips to sc"ools, s"opping centers, residential units, office comple/es, etc #"ic" can t"en 1e used in

transportation planning. 'pecial sur*eys and census can 1e used to collect data on different

socioeconomic c"aracteristics of residents li*ing in a community. 'uc" socioeconomic data include

le*el of income, num1er of mem1ers in t"e "ouse"old, num1er of autos in t"e "ouse"old, num1er of

c"ildren, age of "ead of "ouse"old, and "ig"est le*el of education ac"ie*ed.

De%!ne Go#s n- Ob/e"t!+es

Goals are generali4ed statements t"at indicate t"e desired ultimate ac"ie*ement of a

transportation plan. E/amples of goals statements mig"t 1e, 8T"e transportation system s"ould

meet t"e mo1ility needs of t"e population9 or 8T"e transportation system s"ould pro*ide en"anced

economic de*elopment opportunities9

15ecti*es are more specific statements t"at indicate t"e means 1y #"ic" t"ese goals #ill 1e

ac"ie*ed. For e/ample, t"e goal of meeting t"e mo1ility needs of t"e population could "a*e t"e

follo#ing o15ecti*es associated #it" it7 8Pro*ide transit ser*ice to ma5or mar0ets in t"e region,9

8%educe congestion on ma5or "ig"#ays,9 and 8Promote 1icycle and pedestrian transportation.9

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$oals and o15ecti*es define t"e e*aluation criteria t"at #ill 1e used later in t"e planning

process to assess t"e relati*e impacts of alternati*e pro5ects and strategies. T"ey also pro*ide an

important lin0age to t"e desires and *alues of t"e pu1lic t"at t"e transportation plan is ser*ing.

I-ent!%, S,ste$ De%!"!en"!es or O&&ortun!t!esTransportation planning identifies and prioriti4es t"ose elements of t"e transportation system

#"ere pro1lems e/ist today or #"ere pro1lems #ill e/ist in t"e future gi*en gro#t" in tra*el.

Additionally, transportation planning can also identify areas #"ere significant pro1lems do not e/ist

today, 1ut #"ere c"anges to t"e system can pro*ide opportunities for en"anced efficiency of

operation.

De+e#o& n- An#,e A#ternt!+es

nce t"e planning process "as identified areas #"ere impro*ements are needed,

transportation planners define different strategies t"at could sol*e t"e pro1lem. In t"e past, t"ese

strategies "a*e focused on impro*ements to "ig"#ays, suc" as adding ne# lanes, impro*ing traffic

control t"roug" signals or signing, or impro*ing traffic flo# t"roug" c"anneli4ation.

!o#e*er, ot"er modern strategies t"at can 1e used to sol*e t"e transportation pro1lem

include reducing t"e demand for transportation t"roug" fle/i1le #or0ing "ours, and application of

ad*anced transportation tec"nologies to t"e operation of a road system, 0no#n as intelligent

trans!ortation s#ste"s. 'uc" systems mig"t include net#or0 sur*eillance t"roug" *ideo cameras,

centrali4ed control centers t"at can re&route traffic around incidents, and dynamic traffic control

de*ices t"at pro*ide coordinated traffic signal timings to ma/imi4e t"e amount of traffic t"at can

flo# t"roug" a set of intersections.

E+#ute A#ternt!+es

E*aluation 1rings toget"er all t"e information gat"ered on indi*idual alternati*es and

pro*ides a frame#or0 to compare t"e relati*e #ort" of t"e alternati*es. In addition, e*aluation

includes met"ods for comparing in an analytical #ay t"e relati*e *alue of t"e alternati*es. ne of

t"e most used approac"es is t"e 1enefit:cost ratio, #"ic" compares t"e alternati*es on t"e 1asis of

discounted 1enefits and costs.

DESIGN AND LOCATION O( 1IG12A

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Introduction

T"e earliest forms of roads ("ig"#ays) consisted mainly of "ard trac0s cleared of *egetation

and compacted 1y "uman and animal traffic. T"ese #ere later #idened 1ecause of "ea*ier traffic

and gra*els and 1ro0en co11lestones #ere poured onto t"e trac0s to ta0e *e"icular traffic. E*en

t"ese types of roads #ere found to 1e non&satisfactory in performance to e*er increasing traffic*olume.

In t"e face of modern de*elopment t"erefore, t"e need for more resistant "ig"#ay 1roug"t

a1out t"e idea of alleat"er roads. T"ese roads not only facilitate mo*ement 1ut also pro*ide more

resistant and dura1le trac0s for comforta1le ride.

In igeria today, unpa*ed roads (eart" and gra*els) are mainly in t"e rural areas and farm

settlements #"ile pa*ed roads (fle/i1le and rigid) are mainly in ur1an areas and 1et#een to#ns and

cities.

lassification of %oads

%oads are classified into t"ree groups in igeria7

2. Trun0 A roads

T"ese are federally maintained roads and usually lin0 t"e state capitals to t"e central

administration.

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Ma'or (treet or Ma'or High$a# An arterial "ig"#ay #it" intersections at grade and

direct access to a1utting property, and on #"ic" geometric design and traffic control

measures are sued to e/pedite t"e safe mo*ement of t"roug" traffic.

)hrough (treet or )hrough High$a# E*ery "ig"#ay or portion t"ereof at t"e entrance

to #"ic" *e"icular traffic from intersecting "ig"#ays is re3uired 1y la# to stop 1efore

entering or crossing t"e same #"en stop signs are erected.

*oal (treet or *oal Road A street or road primarily for access to residence, 1usiness

or ot"er a1utting property.

+iided High$a# A "ig"#ay #it" separated road#ays for traffic in opposite directions.

)oll Road, -ridge, or )unnel A "ig"#ay, 1ridge, or tunnel open to traffic only upon

payment of a direct toll or fee.

ul/+e/(a (treet A local street open at one end only, and #it" special pro*isions for

turning around.

+ead/End (treet A local street open at one end only, #it"out special pro*isions for

turning around.

Pr!n"!es o% 1!'45, Lo"t!on

'ome detailed guiding principles s"ould 1e 0ept in mind in selecting t"e location for a

"ig"#ay. T"e follo#ing outline is not in any particular order nor complete. In addition, some of

t"e elements tend to contradict one anot"er; in practice, t"e location is selected #"ic" represents t"e

1est compromise solution.

2. For t"e "ig"#ay to ser*e its function of allo#ing con*enient, continuous, free&flo#ing

traffic operation, it s"ould 1e located #"ere it can 1est meet t"e ma5or traffic desire lines

and 1e as direct as possi1le.

eep grades and cur*ature to t"e minimum necessary to satisfy t"e ser*ice re3uirements

of t"e "ig"#ay.

=. A*oid sudden c"anges in sig"t distance, especially near 5unctions.

?. A*oid "a*ing a s"arp "ori4ontal cur*e on or ad5acent to a pronounced *ertical cur*e.

@. In ur1an areas, site t"e "ig"#ay t"roug" unde*eloped or 1lig"ted areas, along t"e edges

of large par0lands, and in general, a#ay from "ig"ly&de*eloped, e/pensi*e land areas.

. In ur1an areas, locate t"e "ig"#ay as closed as possi1le to t"e principal par0ing

terminals.

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B. In rural areas, locate as muc" as possi1le of t"e ne# "ig"#ay on e/isting ones, so as to

minimi4e t"e use of farmland and reduce total initial and maintenance costs.

C. +ocate along t"e edges of properties rat"er t"an t"roug" t"e middle, so as to cause t"e

minimum interference to culti*ation and a*oid t"e need for su1#ay construction.

. A*oid t"e destruction or remo*al of man&made culture.2. >eep t"e "ig"#ay a#ay from cemeteries, places of #ors"ip, "ospitals, sc"ools and

playgrounds.

22. T"e effect of t"e proposed "ig"#ay on e/isting ro future utilities a1o*e, on or under t"e

ground s"ould 1e considered. It may 1e suc" as to #arrant c"anges in order to a*oid

e/pensi*e relocation of t"ese utilities.

2

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*ariety of engineering, en*ironmental, social, and economic 0no#ledge. T"e type and amount of

data collected during t"is initial p"ase #ill *ary #it" t"e functional classification of t"e road and t"e

nature and si4e of t"e pro5ect.

T"e categories of desira1le data are as follo#s7

2. Engineering datai) Topograp"ic and geological maps

ii) 'tream and drainage 1asin maps

iii) limatic records

i*) Preliminary sur*ey maps of pre*ious pro5ects

*) Traffic sur*eys and capacity studies

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After an e/"austi*e study of topograp"ic maps, drainage maps, soil maps, and ot"er data is

made in t"e office, a series of proposed locations may 1e selected for a field in*estigation.

6!! Re"onn!ssn"e Sur+e,

T"e reconnaissance sur*ey consists of a field in*estigation t"at usually pro*ides a means of*erification of conditions as determined from t"e preliminary des0 study. For e/ample, 1uilding

sym1ols on maps do not indicate t"e true *alues of property under consideration, and t"is

information can usually 1e secured 1y field in*estigation. A study is made of t"e profiles and

grades of all alternati*e routes and cost estimates made for grading, surfacing, structures, and rig"t&

ofay. A comparison of alternati*e routes in t"is fas"ion #ill aid t"e final selection of t"e most

li0ely location.

6!!! Pre#!$!nr, Sur+e,

A preliminary sur*ey is made to gat"er information a1out all t"e p"ysical factors t"at affect

t"e tentati*ely accepted route. In general, a regular sur*ey party carries out t"e #or0. T"e ra# data

is normally ac3uired using some of t"e con*entional sur*eying e3uipment including7

a) Tapes, T"eodolite and le*el

1) T"eodolite and Electromagnetic Distance Measurement

c) om1ined T"eodolite and EDM system

d) Total 'tation

Field s"eets or field 1oo0s are re3uired to record all o1ser*ations 1y "and. Data loggers are

a*aila1le for automatic recording of o1ser*ations #"en Total 'tation is used.

A primary tra*erse or 1aseline is esta1lis"ed as an open tra*erse consisting of tangent

distances and deflection angles follo#ing appro/imately t"e line recommended in t"e

reconnaissance report. Traditionally, con*entional ground sur*eys are carried out 1y t"e use of

T"eodolite to measure angles in 1ot" *ertical and "ori4ontal planes, t"e +e*elling instrument for

measuring c"anges in ele*ations ("eig"ts), and t"e tape for measuring "ori4ontal distances.

!o#e*er, #it" de*elopments in electronics, EDM mounted on T"eodolite or total station can no#

1e used more effecti*ely for most sur*eying pro5ects.

"en t"e preliminary line "as 1een esta1lis"ed, t"e topograp"ic features are recorded. T"e

e/tent to t"e rig"t and left of t"e tra*erse line to #"ic" t"e topograp"y s"ould 1e determined #ill

*ary 1ut s"ould not 1e less t"an t"e proposed #idt" of rig"t&ofay.

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6sing t"e preliminary sur*ey as a 1asis, a preliminary sur*ey map is dra#n. T"e

preliminary map s"ould s"o# all tangents #it" t"eir 1earings and distances, all deflection angles,

ties to property corners, etc. ertain topograp"ic features suc" as streams, #atercourses, la0es,

"ills, and ra*ines, and man&made features suc" as 1uildings, drainage structures, po#er lines, and

ot"er pu1lic facilities are s"o#n on t"e map.

6!+ (!n# Lo"t!on Sur+e,

T"e final location sur*ey is t"e detailed layout of t"e selected route, during #"ic" time t"e

final "ori4ontal and *ertical alignments are determined and t"e final positions of structures and

drainage c"annels are also determined. T"e final location sur*ey ser*es t"e dual purpose of

permanently esta1lis"ing t"e centerline and collecting t"e information necessary for t"e preparation

of plans for construction. T"e line to 1e esta1lis"ed s"ould follo# as closely as is practical, t"e line

dra#n on t"e preliminary map, conforming to t"e ma5or and minor control points and t"e alignment

t"at #as pre*iously determined.

T"e first step in t"e final location sur*ey re3uires t"e esta1lis"ment of t"e centerline, #"ic"

is used as a sur*ey reference line, upon #"ic" property descriptions are 1ased for t"e purpose of

purc"asing rig"t&ofay. +e*el #or0 is of t"e utmost importance, 1ecause t"e grade line,

eart"#or0, and drainage are designed from t"e le*el notes. Finally, cross&sections le*els are ta0en

at inter*als ranging from 2 to @m in t"e trans*erse direction and longitudinally at regular inter*al of

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ustomarily, points along t"e route are identified 1y c"ainages (stations), t"e distance in

metres from some reference point, commonly t"e 1eginning point for t"e pro5ect. T"e location of

points in t"e *ertical plane (or along t"e0&a/is) is gi*en as t"e ele*ation a1o*e mean sea le*el.

T"e cross section of a road#ay is descri1ed 1y its dimensions at a rig"t angle to t"e direction

of t"e alignment, including #idt"s, clearances, slopes, and so on.

A CIRCULAR CUR8ES 9 GENERAL

A "ig"#ay route sur*ey is initially laid out as a series of straig"t lines (tangents). nce t"e

centerline location alignment "as 1een confirmed, t"e tangents are 5oined 1y circular cur*es t"at

allo# for smoot" *e"icle operation at t"e speeds for #"ic" t"e "ig"#ay #as designed.

(!'ure * C!r"u#r "ur+e ter$!no#o',

Figure 2 illustrates "o# t#o tangents are 5oined 1y a circular cur*e and s"o#s some related

circular cur*e terminology. T"e point at #"ic" t"e alignment c"anges from straig"t to circular is

0no#n as t"e (1eginning of cur*e). T"e is located distance T (su1tangent) from t"e PI

(point of tangent intersection). T"e lengt" of circular cur*e (+) is dependent on t"e central angle

and t"e *alue of % (radius).

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T"e point at #"ic" t"e alignment c"anges from circular 1ac0 to tangent is 0no#n as t"e E

(end of cur*e). 'ince t"e cur*e is symmetrical a1out t"e PI, t"e E is also located distance T from

t"e PI. From geometry, t"e radius of a circle is perpendicular to t"e tangent at t"e point of tangency.

T"erefore, t"e radius is perpendicular to t"e 1ac0 tangent at t"e and t"e for#ard tangent at t"e

E.T"e terms and E are also referred to 1y some agencies as P (point of cur*e or

cur*ature) and PT (point of tangency), and 1y ot"ers as T (tangent to cur*e) and T (cur*e to

tangent).

B CIRCULAR CUR8E GEO.ETR

Most cur*e pro1lems are calculated from field measurements (and t"e c"ainage of PI) and

from design parameters (%). $i*en % (#"ic" is dependent on t"e design speed) and , all ot"er

cur*e components can 1e computed.

Analysis of Figure < #ill s"o# t"at t"e cur*e deflection angle (PI, , E) is