Road Network
The road network is the "raison d'etre" of the GIS. Specifying the road
network prior to digitising was commenced on the first day of the study - end of
May 1999. The source material was the list of road sections comprising State
Highways, Major and Other District Roads together with a blue
print(approximately 1:250,000 scale) with roads hand-coloured - National
Highways (NH) - black, State Highways (SH) - red, Major District Roads (MD -
blue, and Other District Roads (OD) - green. The map also contained some
Inter-Village Roads (IV) - yellow. The same colour coding scheme was adopted in
the GIS until recently when Inter-Village Roads are now shown with a black
dashed line to facilitate photocopying the A1 size Manipur and individual
district maps. The coloured blueprints did not show the precise specification of
all the road sections on the list.
Being blueprints the base maps had
become distorted over time. Furthermore the alignment of the roads was imprecise
- one only has to look at the alignment of roads on the 1:250,000 Map Sheets
compared to the same roads on the 1:50,000 toposheets.
The first task
was to sub-divide the specified Road Sections into links. Each link was
allocated an Unique Link Identifier referred to as the LinkID. eg SH10.12 a link
which is part of the Road Section numbered 10 in the list of State Highways. For
example links making up SH10 were allocated LinkIDs - SH10.10, SH10.12, SH10.14
…………… SH10.24 from start of the section (SH10.10) to the end of the section
(SH10.24). The numbers start at 10 and increment by 2; incrementing by 2 allows
an additional link to be inserted between two original links without affecting
the sequence.
The links in the road network are stored in two tables -
MAINroads - NH, SH, MD, OD and IVroads - InterVillage Roads. Nodes have been
specified at the end of or at the intersections of roads in the Main Road
Network. Nodes are not specified on Inter-Village Roads. The fields in the
MAINroads table are :-
- DIST - District
- CLASS - Class (NH, SH, MD, OD)
- RS - Road Section
- RSdesc - Road Section Description
- RSlength - Road Section - Length (as specified on the list of roads)
- RStype - Road Section - type of construction
- RScond - Road Section - condition of road (from PWD records)
- RSwidh - Road Section - road width
- LinkID
- NA - node number at start of link
- NB - node number at end of link
- LEN - Length of link derived from the GIS. (using the function
SphericalObjectLen)
- GPSlen - Length of Link derived from GPS outputs from a drive along the Road
Section)
- Terrain - Type of Terrain
- Flow - Traffic Flow
- Capacity - Link Capacity
- Rwidth - Road Width (from Strip Plan Survey where available)
In
the table IVroads the fields RS, RSdesc, RSlength, RStype, RScond, RSwidth are
dummy variables and are blank. As nodes are not specified on Inter-Village Roads
NA and NB are also dummy variables and are blank.
The initial link
digitisation was based on 1:250,000 scale blueprints, this was later refined
using individual district blue print maps. These maps proved to be inconsistent
and the current digitisation is based on the 1:50,000 toposheets The roads
having been drawn on photocopies of the toposheets .by the PWD Engineers with
the most detailed knowledge of the districts. Checking and amending road
specifications is a continuous process.The Road Network is shown in Figure 2 and
the detailed coding in Figure 3.
An additional table - LinkIRI has been
created from the Bump Integrator Survey which was carried out along the Road
Sections selected for the Feasibility Study on a chainage basis - one estimate
of IRI for each kilometre was recorded. In LinkIRI the average IRI for the link
together with range of IRI values along the link are stored.
A further
table STRIPplans relates Strip Plan Drawing Numbers to LinkIDs.
Public TransportThe GIS includes information on Inter-State Bus
Services, State-wide Services and District-wide Services. The main sources of
information were :-
- Directorate of Transport (responsible for regulation)
- Interviewing private firms - mainly for Inter-State/ Tourist and the Sumo
Services to extremities of the State.
- Interviewing officials, bus/truck/jeep/van/auto-rickshaw drivers and
passengers, other members of the public whilst on traffic surveys and road
reconnaissance tours.
- Meetings in Towns and Villages
- Ad hoc meetings with PWD engineers, NGOs and members o the public in our
office or at presentations.
Each State-wide service was allocated an
Unique Identifier such as DML1, DML2, BSR1 where DML and BSR are the standard
abbreviation of the "lines" and each District Service was allocated an Unique
Identifier such as IMPL1,IMPL2 where IMP is the standard abbreviation for Imphal
District and L indicates a local service. There are only two Inter-state
services which were assigned codes EXT1 - Imphal to Dimapur/Guwahati & EXT2
- Imphal to Silchar.
The whole public transport system comprises two tables
- PTservices and PTroutes. PTservices contains a row for each service containing
the Unique Route Identifier, the Operator, Description (eg Chandel to Sugnu),
Mode - bus, mini-bus, truck, jeep/gypsy, van, auto-rickshaw, sumo, the number of
vehicles plying the route per day. PTroutes contain for each stop on a route the
Unique Route Identifier, the Unique LinkID of each link in the road network that
the bus route serves and the sequence of that link along that route (ie first
link, second link etc.). The Unique LinkIDs enable public transport information
such as individual routes, the number and type of vehicles traversing/ servicing
each link to be displayed geographically. Figure 4 shows the public transport
route system Using the Table containing village demographic information the
accessibility (or non-accessibility) to public transport can be assessed.