8.  INFRASTRUCTURE FACILITIES

8.1 Transportation Facilities

8.1.1 Hierarchy of Roads

The road hierarchy in residential areas comprises arterial, collector, minor, access, and minor access roads:

Arterial Roads:

An arterial road serves to carry through-traffic between districts and communities and should not pass through subdivisions. The number of points of intersection of arterial roads with collector roads should be kept to a minimum.

In cases where a proposed subdivision is adjacent to an existing or proposed arterial road, layouts should be designed to separate as far as possible arterial roads and local traffic and to minimise the effects of arterial traffic on the residents.  Figure 8.1 illustrates typical street designs used in site layouts.

Collectors:

Collector roads provide for the movement of traffic between major arterial roads and internal access streets. The design of junctions between collector and arterial roads should therefore be such that safe entry to and egress from the subdivision is facilitated.

Collector roads should not be less than 45 metres apart, and should be designed and laid out so that their use by through-traffic is discouraged. The design capacity of these roads should facilitate the safe and efficient movement of traffic generated by the subdivision.

Collector roads may provide direct access to certain properties within the subdivision. However, the number of such properties should be kept to a minimum.

The construction of collector roads is the responsibility of the developer.

Minor Roads:

Minor roads provide direct access to properties and in addition serve as connecting links to other roads in the subdivision.

Access roads are intended for use by local traffic and to provide direct access to residential properties.

The construction of access roads within a subdivision, is the responsibility of the developer.

Minor Access Roads:

This would take the form of a cul-de-sac serving a maximum of twelve (12) residential units.

8.1.2 Street Intersections

Three-way junctions are preferred to four-way intersections at minor roads within a subdivision.  Major four-way intersections may be controlled by adequate traffic signals since there are more possible turning movements and greater potential for accidents with this type of intersection than with the three-way junction.

Clear sight lines should exist across the angles of intersections and/or where the direction of the road changes vertically or horizontally.  To ensure the adequacy of sight lines for turning, no angle of intersection of roads within new development should be less than 60⁰ (Figure 8.2).  Also junctions and intersections should not be located at the crest of a slope or incline.

Intersections which connect more than two roads should be avoided where possible, since they increase turning movements and the possibility of traffic accidents.

8.1.3 Right of Way and Carriageway Widths

Access routes within a subdivision should conform with standards relating to the minimum right-of-way and carriageway width and the maximum gradient of the land on which they may be constructed.

The minimum right of way width is the minimum area which must be reserved for carriageways, verges, and sidewalks. The minimum carriageway width is the minimum allowable width of the paved portion of the road designed for vehicular traffic. Maximum gradient is the maximum allowable (steepness of the) slope on which the road may be constructed.

The standards which are applied to access routes within a subdivision are determined by:

• Function of the access route
• Size and residential density of the development
• Topography of the site.

Width and gradient standards for access routes are intended to ensure that these routes can safely accommodate the volume of normal traffic that will be generated by the subdivision and to facilitate the movement of service vehicles. Table 8.1 specifies the minimum width and maximum gradient standards for access routes within subdivisions located on various types of terrain. Typical cross sections for the hierarchy of residential streets are illustrated in Figures 8.3 and 8.4.

At all intersections, curb cuts should be constructed so that disabled persons may safely use the streets and sidewalks.  These cuts should be built using materials which provide a non-slip surface and are easily identifiable by visually handicapped persons.

8.1.4 Cul-De-Sacs

The length of cul-de-sacs should not exceed 150 metres and the width of the reserve no less than 8m.  Culs-de-sac should not normally service more than 20 residential plots. The design of turnarounds at the end of cul-de-sacs should be such that fire fighting equipment and service vehicles should experience minimum difficulty of maneuvering.  The calculation of turning radii for cul-de-sacs should conform to established engineering standards.

Where it is needed or desirable, a two-metre reserve at the end of cul-de-sacs would be required to provide for the construction of pedestrian ways into the next street, or as a utility corridor.

Typical cul-de-sac designs are illustrated in Figure 8.5.

8.1.5 Street Furniture

The use of street furniture such as benches, lamps, and bins contributes to a visually appealing streetscape as well as to an environment which is clean, safe, and functional.  Materials used for street furniture should be durable enough to withstand weather conditions and constant use.  Street furniture should be located so as not to obstruct sight lines at intersections and pedestrian crossings.

Street nameplates should be well designed and clearly lettered.  They should be placed not more than 3 metres from street corners and between 1.5 metres on walls and 2 metres on poles above the ground.

Fire hydrants should be located 1.25m from the curb and outside of property boundaries.

Table 8.1:Desirable Standards for Design of Streets

in Residential Subdivisions

Notes:  

(1) Terrain Classification:
        Ordinary: Cross slope range    0 per cent to 8 per cent (0 to 1: 12)
        Rolling: Cross slope range       8.1 per cent to 15 per cent (1: 12 to 1:7)
(2) Development Intensity: (in terms of gross density of land area).
   Low: 3 units or less per acre: Medium: 3 to 7 units per acre      High: Over 7 units per acre
(3) Right-of-way width may be increased in hilly terrain to accommodate side slopes.
(4) Carriage width includes slipper drains.
(5) Maximum gradients may be exceeded for short lengths of road, subject to approval.

FIGURE 8.3
CROSS SECTIONS OF ROADS

FIGURE 8.4
CROSS SECTIONS OF ROADS

FIGURE 8.5
CUL-DE-SAC DESIGNS

FIGURE 8.6
CAR PARKING DIMENSIONS

8.1.6 Parking

The number of on-site parking spaces required on individual sites will be determined by the nature and scale of the activity being conducted in the context of the overall land use and transportation policy for the wider area. In certain circumstances, consideration may be given to the provision of off-site parking facilities in the vicinity of the development site.

Basic guidelines for the provision and layout of parking facilities are as follows:

1. Parking spaces for single-family dwellings should be located within the curtilage of each residential plot.  Parking spaces for multifamily residential buildings may be located immediately adjacent to individual units or in grouped parking lots.
   
2. Parking spaces for non-residential uses may be grouped in lots at grade or above or below ground level.  These parking areas should be sited so that they are easily accessible to users.
   
3. Where appropriate, parking areas should be screened by fences, trees, shrubs, or berms in order to minimise the adverse effects of traffic noise and visual intrusion, especially where parking areas abut residential development.
   
4. Parking spaces should be provided for physically disabled persons in all public buildings. Pedestrian ramps should be constructed to provide access into the buildings.
   
5. Parking spaces should be located and designed so that vehicles can enter and leave the car park in a forward direction.  Each parking space should be provided with proper access to facilitate entry to and egress from that space.  The dimensions of a standard car parking space are 2.5 metres by 5.5 metres (Figure 8.6).  The land area allocated for each car space inclusive of aisle and circulation space should be between 20m² and 30m² depending on design and site characteristics.
   
6. Parking spaces may be provided at angles of 90⁰, 60⁰, 45⁰, or parallel to the aisle (Figure 8.7).  Where parking spaces are provided at 90⁰ or 60⁰ to the aisle, the minimum width of aisle for two-way traffic shall be not less than 5.5 metres.  At angles of less than 60⁰ the minimum width of the aisle shall be not less than 4.0 metres and traffic flow shall be one way only.

8.1.7 Loading

Where it is proposed to erect a new building or to extend an existing building for retail, industrial, warehousing, or other uses which generate truck or container traffic, provision must be made for parking, circulation, and loading/unloading of goods vehicles.

FIGURE 8.7
PARKING LOT LAYOUT

The loading standard specifies the minimum number and the dimensions of bays which are to be provided within the curtilage of the site for the servicing of goods vehicles.  Standards for the provision of loading bays will be determined by the nature and scale of the proposed activity and the location of the development.  The dimensions of a loading/unloading bay are normally 3.5m x 7.0m. However it may be necessary to provide additional space to cater for large goods vehicles or containers.

8.2 Water Supply

The Water and Sewerage Authority (WASA) is the agency responsible for providing an adequate supply of potable water. Developers are however responsible for providing acceptable water distribution system to serve individual plots within their developments.  These systems must meet the performance standards and requirements of WASA and receive the required approvals prior to commencement of development.

For comprehensive developments involving both land development and construction of buildings, the developers will be responsible for laying out the main water distribution systems as well as connecting links to individual properties.

8.3 Sewage Disposal

The more common methods of sewage disposal in Trinidad and Tobago include:

1. Water-Borne Sewerage Systems:
   For any development located in an area where such a system is available, the developer will be required to provide connecting sewers from the central system to the individual plots.
   
2. Septic Tank and Soakaway/Septic Tank and Absorption Trench/Septic Tank and Filter Trench Systems:
   These facilities may be used for one-lot and small residential developments located in areas where a water-borne system is not available. The particular system to be utilised would depend on the soil characteristics of the area.
   
3. Pit Latrines:
   This may be the only method of sewage disposal available in rural areas which do not receive a regular supply of pipe borne water. The pits must conform with standards of design and maintenance as established by the Local Health Authority.
   
4. Sewage Treatment Plants:
   The need for a sewage treatment plant is generally determined by the size and location of a development, the size of individual plots within the development, existing soil conditions, and any other relevant considerations.
   Sewage disposal systems must conform with standards established by the Water and Sewerage Authority with regard to capacity, design, construction, and maintenance. Approval from WASA would be required prior to the commencement of development.
   
   Adequate land area must be provided within any development for sewage disposal systems, and such areas should be clearly identified on plans accompanying applications for planning permission.
   
   The location of sewage treatment plants in a development should not adversely affect the enjoyment of surrounding properties.  Adequate screening should be provided between the plant and other uses within the development.

8.4 Drainage                                   

The Drainage Division determines and administers standards for storm water drainage in development projects. The drainage system for any development must meet the standards and specifications of the Drainage Division prior to the commencement of development.

The developer is responsible for installing the drainage system to provide adequate drainage for his development.  The drainage system in any development must be integrated with the overall drainage system on adjoining lands to avoid any adverse environmental effects. The drainage outfall must however be to the public drainage system and not through adjacent private lands.

8.5 Solid Waste Disposal

The collection and disposal of solid waste is the responsibility of the relevant local government authority.  However, adequate provision must be made by the occupant or the developer for the holding of garbage prior to collection. Specifications can be obtained from the Local Health Authorities.

8.6 Electricity

The Trinidad and Tobago Electricity Commission (T&TEC) is responsible for the provision of electricity service.

Where electricity service is required, it is recommended that developers consult T&TEC prior to development in order to ascertain whether the site can be adequately supplied.  This is particularly important for areas which may not have been supplied with electricity in the past and for large scale or high intensity development.

It is to be noted that in certain developments provision may be required for the installation of substations.

Wherever feasible, power lines and cables should be laid underground in the road verges to improve the appearance of the development and to reduce the risk of wind damage during storms.

8.7 Telecommunications and Cable Television

Telecommunications Services of Trinidad and Tobago Limited (TSTT) provides telecommunications services. Developers should make early contact with the company prior to development in order to arrange for the service.

Cable television service is provided by a number of cable television companies operating in various parts of the country.

As in the case of electricity service, telephone and cable television lines should be placed underground wherever feasible.

8.8 Maintenance of Facilities

All infrastructure facilities in a development should be regularly maintained in order to ensure that they function in an efficient manner and to protect the health, safety, and convenience of the community.