SUPPLEMENTAL COMMENTS ON

PROPOSED MUTCD REVISIONS

DOCKET NO. FHWA-2007-28977

Submitted by Ken Stevenson

2050 Moonstone Way

Sacramento, California 95835

<ken.r.stevenson@gmail.com>

After viewing comments submitted by others, I would like to expand on
the comments I previously submitted (comment no. 1813.1) on proposed
section 2E.20 -- Diagrammatic Signs.

A number of commenters objected to the proposed arrow-per-lane design
for diagrammatic guide signs, and recommended that the current
map-graphic design be retained. If, in response to the concerns, FHWA
retains the current design, I believe its effectiveness could be
improved with revised or additional guidance from FHWA.

In my initial comments, I discussed how the execution of diagrammatic
guide signs is often less than optimal, and provided some examples. Some
of the shortcomings I've noted include:

-   The signs contain too much legend for a driver to reasonably absorb,
    often because the signs depict interchanges that are too complex
    (have too many ramps and destinations).

-   The signs depict the number of lanes at the interchange, but this
    differs from the number of lanes at the sign's location, preventing
    the driver from determining with certainty where the current lanes
    go.

-   The signs are not well-executed. Specifically,

    -   Lane lines are faint, parallel lane lines are not aligned, or
        lane lines do not clearly depict which lanes lead to each
        roadway.

    -   Lanes on the arrow are too narrow.

    -   Lanes do not have a consistent width.

    -   The legend is not closely aligned with the associated arrowhead.

    -   The signs don't accurately depict the number of lanes at either
        the interchange or the sign's location (e.g., showing a 3-lane
        roadway as having 2 lanes).

-   Signs are used where not needed (such as at a right exit without a
    lane drop).

-   Roadway curvatures are precisely depicted in locations where this
    information is unnecessary (i.e., places where there would be no
    need for curve warning signs).

Sometimes, the problems result from not following the guidance in the
Standard Highway Signs Book, but this isn't always the case. I suggest
that FHWA consider making the following revisions or additions to the
Standard Highway Signs guidance:

-   Specify a wider lane line (currently, 1 inch) and/or a higher
    line-to-gap ratio (lines longer than gap) (currently 1:1, line and
    gap both 6 inches).

-   Specify a wider lane (currently, 5 inches) and emphasize the need to
    consistently apply this dimension to all lanes depicted (see *Figure
    5* for an example*)*.

-   Discourage the use of oversized arrowheads (a common distraction).

-   Discourage precise depictions of roadway curvatures (except where
    curvatures are extreme -- such as with loop ramps -- and it is not
    feasible to provide this information through conventional means,
    such as ramp speed signs). Use a straight-up arrow shaft for the
    "ahead" direction, and straight shafts at +/- 45 degrees for the
    ramps, minimizing the curve of the shaft at the gore.

-   Keep parallel lane lines and gaps aligned as much as possible.
    Around curved shaft segments, vary line lengths to achieve this on
    the straight segments.

See *Figure 1* for an illustration of a sign designed using these
guidelines. (Note that the illustration violates current guidance --
multiple ramps, multiple destinations for one direction -- but the
reality is that these guidelines are often not strictly adhered to.)

Although I think that these changes would improve the effectiveness of
the current design in conveying lane assignment information, I believe a
"hybrid" format -- utilizing elements of the current and proposed
formats -- might be even more effective. It would use the current
format, except that individual lane arrows would be substituted for the
"map" graphic. This should significantly improve legibility and also
reduce the potential for diminishing legibility through poor execution.
See *Figure 2* for an example. The improved legibility of the Figure 2
design can be demonstrated by greatly reducing the size of the figures
on the computer screen (simulating viewing the signs at a distance) and
comparing the two figures. At a certain point, the lane lines on the
map-graphic disappear; at this point, the individual arrows are still
visibly distinct.

While the map-graphic guide sign could be improved, the arrow-per-lane
design (with the individual arrows located over each lane) would likely
be even more effective, and I encourage FHWA to adopt the proposed
design, at least as an option. However, concerns have been raised about
the feasibility of the design, primarily because the signs would have to
be very large to accommodate arrows of the prescribed dimensions. To
address these concerns, FHWA might consider changing the proposed arrow
specifications to something like that used in Australia, which would
allow a smaller sign to be used (see *Figure 3.* In my opinion, the
Australian arrow design could be improved; see *Figure 4.*)

***Figure 1***

![](media/image1.png){width="5.997222222222222in"
height="3.071527777777778in"}

***Figure 2***

![](media/image2.png){width="5.998611111111111in"
height="3.076388888888889in"}

***Figure 3***

![](media/image3.jpeg){width="4.988888888888889in"
height="2.9409722222222223in"}

***Figure 4***

![](media/image4.png){width="3.9965277777777777in"
height="2.5590277777777777in"}

Three additional examples of diagrammatic guide sign designs from other
countries are shown on the following page.

*Note: Figure 7 from skyscrapercity.com; all other figures by the
author.*

***Figure 5 -- Canada.*** The very legible map graphic on this Toronto
sign has wider lanes than are normally seen on U.S. diagrammatic signs.
Note that the sign is also lower and smaller than the typical U.S.
diagrammatic sign.

![](media/image5.jpeg){width="4.741666666666666in"
height="2.688888888888889in"}

***Figure 6 -- Denmark.*** Clustered lane arrows on post-mounted signs.

![](media/image6.jpeg){width="4.753472222222222in"
height="2.651388888888889in"}

***Figure 7 -- South Africa.*** Clustered lane arrows on an overhead
sign.

![](media/image7.jpeg){width="4.750694444444444in"
height="2.4784722222222224in"}