JUNCTION IMPROVEMENT WORKS UNDER TSM

INTRODUCTION

TSM, the acronym for Traffic System Management, cannot be ignored if the city of Lagos is to enjoy an improved traffic flow. Many roads in Lagos lack traffic vertical and horizontal signs and where they exist, the signals are obsolete, dysfunctional, or inadequate.  This makes the traffic scenario on traffic junctions, chaotic and at best, confusing.

TSM junction improvement measures under the auspices of the Lagos Metropolitan Area Transport Authority (LAMATA), amongst other such efforts, are an intervention to improve some of the junctions in Lagos State.

Daleko junction, Iyana Isolo junction before rehabilitation

Daleko junction, Iyana Isolo junction after rehabilitation

Impact of TSM Measures/Junction Improvement on Junction Traffic Flow
The Lagos Metropolis is replete with intersection of roadways without control devices.
When the road signs and other TSM measures on a Sign-controlled junction are dysfunctional, ineffective, inadequate, or not enforced nor not obeyed, the junction translates literarily to an uncontrolled junction. On the other hand, an existing sign-controlled junction may migrate to a signal-controlled one, if the necessary operating conditions so indicate.
The absence of signs for effective control of traffic through the junctions makes the through-traffic rowdy. The implications of these are not far-fetched; delays, high accident potential and risks to vehicles and pedestrians, bottlenecks or traffic hold-ups especially at peak periods and an aesthetics mess to say the least. The remedy therefore is in specific junction study, aimed at scientific evaluation of the problems, potentials and possibilities in terms of various TSM measures that can be put in place to remedy the problems and put the full potentials of the junctions to use.

The Present situation in Lagos
Lagos, the commercial nerve center of Nigeria has the potential of a Mega-city status.
Understandably, the traffic scenario in mega cities grows with population, sometime beyond the bounds of earlier predictive and speculative designs.  The situation calls for regular reviews, data gathering and design reassessment to combat perennial congestion, and traffic bottlenecks on Lagos roads.  Of particular interest is the traffic scenario at crossroads otherwise known as junctions.
The situation is not helped by absence of clear-cut control mechanism, jay-walking on the junction right of way, illegal vehicular loadings and off-loadings at junctions coupled with the influx of commercial motorcycle parks attracted to the junctions by virtue of insufficient and sometimes inefficient public transit systems to cater for increasing teeming population of pedestal Lagosians.
Added to this, junctions in Lagos are gradually becoming hot spots for commercial activities. Inadequacy of current design state of junctions and absence of Traffic System management measures have made most Junctions counter-productive.

Major challenges at most Lagos junctions:
i. Loading and off-loading of commercial vehicles at the junction
ii. Illegal Commercial Motorcycle park which reduces carriageway capacity, hinders easy traffic flow
iii. Absence of functional street lights for clear visibility and safety at night.
iv. Absence of vertical traffic signs.
v. Absence of lane-markings and worded messages.
vi. Pedestrian encroachment of vehicles at the bridge abutment, which poses pedestrian-vehicle accident risks.
vii. Walkway taken over by private developments on both sides of the Access road. This encourages pedestrian encroachment to the right of way of vehicles and poses pedestrian-vehicle accident risks. 
viii. Absence of pedestrian crossings on the Access road. This encourages uncontrolled pedestrian-vehicle conflict and accident risks.
ix. Absence of drainage system especially on the approach to the main junction from the Access road. This explains why some portions of the walkway are in a state of disrepair. This problem is a subset of the general drainage problems causing perennial flooding and pavement deterioration.
 
TSM STRATEGIES
Assess Road Condition:
a. Level of deterioration of road pavements
b. Encroachments: Pedestrian, Automobile and Motorcycles
c. Sight stopping distance
d. Lane Markings
e. Pedestrian Crossing
f.  Walkways
g. Drainage Facilities
h. Kerbs

Existing Traffic Control Measures
a. Type of Control(s)
b. State of Control

Existing TSM Measures on Junctions
a. Inventory of vertical signs
b. Inventory of horizontal signs
c. Serviceability of road signs
d. Condition of road markings
e. Stop-lines

Existing Encroachment on Junctions
a. Pedestrian Encroachment level
b. Automobile Encroachment level
c. Motorcycle Encroachment level
d. Utilities obstructing flow of traffic

Physical Junction Conditions
a. Junction Pavement
b. Drainages
c. Walkways
d. Lay-byes / Shoulder widths
e. Channelization / Islands
f.  Median Characteristics
g. Median Conditions

Junction Furniture
a. Lightning

General Signs
The general categorizations of all signs are:

a. Informatory signs: These will be used to provide directions to motorists, including route designations, destinations, available services, point of interests and other geographic, recreational or cultural sites.

b. Regulatory Signs: These will be used to impose legal restrictions applicable to particular locations and unenforceable without such signs.

c. Warning Signs: These will be used to call attention to hazardous conditions, actual or potential, that would otherwise be readily apparent.

Guidance for Basic Sign Design
The basic design of these signs shall be guided by the following Specifications.

i.   The sign Attention Value
ii.  Legibility
       a. Pure legibility   
       b. Glance legibility
iii. Recognition

Standard sign shapes, color, and message of signs in consonance with approved specifications of Federal Road Safety Corps (FRSC) of Nigeria are adopted.

Horizontal Signs: Typical horizontal signs include potential horizontal sings to be considered include:
• Directional Arrows
• Solid and broken lines
• Worded sign
• Kerb painting

JUNCTION IMPROVEMENT STRATEGIES
• Localized carriageway hindering
• Shoulder improvement
• Provision of pedestrian refuse
• Junction widening
• Provision of Lay-byes
• Improvement of Property Access
• Pedestrian Crossing Points
• Provision of road humps, rumble strips and raised junction
• Provision of walkways; barriers and road crossing facilities
• Provision and painting of kerbs
• Rehabilitation of approach roads (where necessary)
• Road lighting
• Improvement landscaping planting or relation of street furniture
• Upgrading of existing signal controls, provision of light signals with pedestrian   phases
• Provision of traffic signals at new and existing priority junction
• Surface dressing and patching of junction pavements
• Provision of drainages

Junction Design Criteria
Efficiency, safety, speed, cost of operations and capacities of junctions depend on the design. Movement from and to various approaches of a junction can be highly facilitated by virile geometric design, optimal traffic control mechanisms as well as appropriate and adequate Traffic System Management measures.

Five basic elements to be considered in such designs are:
• Human factors
• Traffic considerations
• Physical elements
• Economic factors
• Functional Junction Area

As contained in Mn/DOT Traffic Engineering Manual, MN MUTCD, Highway Capacity Manual and AASHTO’s policy on Geometric Design of Highways and streets. Other junction design criteria include:
• Desirable Traffic Controls (name, signs, signals, pavement markings)
• Capacity Analysis (Level of service, number of approaches lanes and turning lanes)
• Degree of access control for highway facility
• Pedestrian Traffic
• Bicycle and Motorcycle Traffic
• Lightning’s Warrants