Trail Bridges
The longer a trail or boardwalk is, the higher the
likelihood that it will need to cross a stream, street, highway, boulder field,
or scree slide area.
Crystal River Preserve
fire road and trail cross the slow, low volume flow of Deer Creek.
Smaller loads allow
for simpler structures. Higher clearance requirements, higher moving “live”
loads, or heaver traffic like ATV’s or service vehicles require more elaborate
structures.
Water crossings typically call for a specifically designed
structure based on water depth and speed, water volume including highest flood
or tide considerations, and posted trail traffic type. A multi-use trail and
fire road might only need a few metal or plastic culverts to cross a small
season stream of low volume. Many boardwalks continue over small streams with
no change in height, materiel, or bracing.
Floating dock at Mobbly Bayou Preserve in
Oldsmar Florida
Transitions to a floating dock in tidal or seasonally
changing water levels involve a “rolling bridge”. This is fixed to the land side boardwalk with
a hinged attachment flap that allows up and down axis movement. The bridge then
touches on the free-floating dock with metal wheels on metal plates. The dock
has caged piers or pilings that allow it to float up or down on the changing
water level. The dock can only go up or
down, but not side to side. The bridge can change angle to match the dock
height by rolling along the long axis of the dock.
Pinellas Trail
crossing a surface street in Bellair.
Crosswalks are marked surface level crossings of streets,
driveways, or other trail types. Signage to delineate the crossing, including
trail marker blazings are typically present.
The higher the volume of traffic, the more elaborate and numerous the
approaches, warning signage, pavement markings,and use restriction signs and
devices become.
Steel trail
overpass at a busy intersection.
Small service vehicles and police motorcycles
use this overpass as well as bicycles and foot traffic.
Busy streets and busy trails are best dealt with using trail
overpasses. Although expensive, they save lives, do not interrupt traffic flow,
and avoid signage costs.The higher clearance requirement, higher volume moving
“live” loads, and heaver traffic like patrol or service specialty vehicles
require this more elaborate structure. This metropolitan area is close to
parks, beaches, and salt water estuaries that attract thousands of users a day.
There is traffic to two mega-shopping areas and a VA Hospital adjacent and a regional mall
and a marina nearby. The county invested in this structure instead
of a crosswalk.
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