The Street Tree Effect and Driver Safety

The trees should be best suited to the climate and the soil. Roadside tree must be fairly Hardy and robust, those can we stand winds and storms. The tree must be shady but not sending out large branches.Too Rapid growing trees should be avoided as they are invariably short- lived and have very brittle branches.The species selected must be either truly evergreen such as mango, nearly evergreen such as the margosa or be in leaf during summer.

Important points :_

1. Trees that develop straight and clean trunk up to a height of about 3 to 3.6 m from the ground level and then spread out are suitable. 
2. All species of trees having large and thick leaves should be avoided as they are required more moisture then the small leaved varieties. Tree with small sized thin-leave  like the tamarind and the margosa stand draught very well as they need much less water than the large and thick leaved varieties.
3. Trees with valuable fruits or wood  and trees like Babul which shed throns. or those requiring much care and water for growing, are not suitable for roadside planting. Those trees which shed their leaves during April and May months are not very not also suitable.
   
4. The nature of the road has also to be taken into consideration selecting the type of trees for planting. where houses are proposed to be built close to the road or on narrow roads, thick growing large trees are not suitable.
5. Trees dry up the soil in summer and reduce the volume of subgrade which may be up to 6 percent, and thus drop  the road surface and crack it. In heavy clay soils keep fast-growing trees at least 15 metre away from the road.
6. Do not plant tree of in incongruous habits together, e.g. banyan and babul or cork tree.It is preferable to have mix planting e.g. trees of different varieties, so that the plants flower and bear fruits in different season and shedding of leaves take place in different part of the season. 
   
7. Tree should be planted 1.8 to 3 metre away from the outer edge of the side width (berm) or, min:horizontal clearance should be 6.7 m for single Lane roads increasing clearance by 1 metre for each  additional lane width. Row on opposite side of road should be staggered.
8. The trees must not interfere with the traffic on the road and should have stemps free from branches for a height of 2.4 to 3 m on highway and 2.7 to 3.3m in streets of towns.
9. Telegraph and telephone or electric lighting poles should we fixed normally at least 1.5 m outside the existing Road edge, and if possible at the road boundaries, so as not to interfere with tree growth by Loppings.
10. No tree should be planted by the roadside before it is 1.5 m high. most of the failures in roadside planting is due to the use of two small Seedlings or of trees which have not had their roots formed by being transplanted in the nursery.

Suitable spacing of trees

Suitable spacing for roadside trees is from 9 to 15 metre according to the species of trees; the average been taken about 80 trees is in a kilometer. the distance apart, However, should not be less than the diameter of the Crown of a fully developed tree, and most of the tree will be about 9.15 metre apart

No trees should be planted within 6 metre of any masonry work on these distance should be increased to 24 metre with trees of spreading root suggest such as pipal,gular,pikhan and bargad.

Suitable spacing :

Banyan	12 M	Mahwa	12-15 M
Bahera	15 M	Mango	12 M
Indian Cork	6 M	Neem	10 M
Jamun	12-15 M	Pipal	17 M
Karanj	10 M	Siris	12m
Khirni	12 M	Teak	14 m