Civil / Roads
Civil / Sitework
Road Design States are roughly divided on use of km or
Sitework, such as location and placement of utility feeds,
100 meter stations. AASHTO recommends km stations.
is among the easier portions of work to do in metric.
Projects may use either at this time.
Surveyors already work in decimal units, and most field
personnel indicated switching to metric involved little if
Use AASHTO Standard R1, equal to ASTM E380, for
any effort.
metric practice.
Our regional electronic surveying and mapping
Federal Highway Administration directed that all
equipment provides data in metric. Many states also
construction using federal funds after October 1996 must
utilize electronic data measurement (EDM) equipment
be designed using the metric system.
which almost always can work in metric units.
The state response has been decisive in many areas, as
Civil / Surveying
many states have established dates earlier than that,
setting dates in 1995, after which their highway
Two primary agencies producing survey data are
construction will be metric.
National Geodetic Survey (NGS) and US Geological
Survey (USGS). SI database information is available.
Many major state and local highway projects starting
now or in the near future are being done in metric.
NGS horizontal and vertical control point network has
been SI since 1983. Benchmark elevations are meters.
Federal, state, and local agencies are already doing
metric road and bridge design, with some already in or
UTM and State Plane Coordinates Systems are metric.
near construction.
Almost 40 states have adopted metric in their state plane
Most states have begun converting standard drawings
coordinate systems.
and specifications to metric. See M1 for details.
See the Road Design Data section for more detail.
Project Data
Right of Way (R/W) Critical issues appear to be public
Most engineers are now using meters for survey
response to SI, and legal acceptance. Our site
elevations, contour intervals, and large scale site
acquisitions, ie r/w purchases, should use technique 1
drawings. Feel free to use m or mm.
below, unless not possible, then use technique 2:
Convert benchmarks from feet to m or mm.
1. Hard Metric Only:
100 m
Ex, 314.15 feet becomes 95.753 m (95 753 mm)
2. Hard Metric / Soft English: 100 m (328.08')
With method 2, when SI is used exclusively, english can
Smart Technique We have seen large mapping scales
be deleted and numbers will be even metric.
use SI symbols. 1:2000 was written as 1:2k, 1:5,000,000
as 1:5M.
This of course applies only to site acquisitions of
uniform geometry (ex, long stretchs of 100 m wide r/w)
For site acquisitions of uneven geometry, SI and english
dimensions will often involve uneven numbers.
We use AASHTO 1993 Guide To Metric Conversion,
for geometric design values, lane and shoulder widths,
curb heights, sight distances, curvatures, other material.
Phone Orders: AASHTO 202-624-5800
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