The following are comments on the proposed amendments to the Manual on Uniform Traffic Control Devices (MUTCD) by the Federal Highway Administration. Referring to the draft proposal will probably improve your comprehension of the comments. - Chris
Many of these comments address the use of metric signage practices. Since there is little current metric signage in the United States, it is important that we get this right now, as opposed to decades down the line when partial or full metrification is mandated by the state or federal governments, or the admission of additional states that traditionally use the metric system requires widespread adoption of the metric signage specified in the MUTCD.
This revision still uses the wrong fontset in many illustrations of signage. The FHWA font series specified in Standard Highway Signs should be used throughout.
As a corollary to this, the FHWA should ensure that a royalty-free outline version of each typeface in the FHWA font series is produced, including proper character metrics, and made available to transportation agencies in OpenType/TrueType and PostScript Type 1 font formats, to further encourage widespread use of proper signing practices.
I strongly recommend that the MUTCD require agencies that install regulatory metric signage (including speed and weight limits) to also include signage with traditional measures for at least ten years after the first posting of the metric signage, except in jurisdictions where signage was posted in metric as of January 2000 (such as Puerto Rico). This would provide a suitable transition period and be far less confusing to motorists than the wholesale elimination of traditional measures from signage.
W1-1a, W1-2a, and W1-13a should include the km/h indication if metric units are used.
As a corollary to this and other metric comments: when other countries transitioned to the metric system, they used "km" instead of "km/h" in speed signage, and placed this designation within the circle, to the right of the number, rather than below it. FHWA should consider adopting this convention, as it would better reinforce the connection between the number and the units it is presented in.
For example, a speed limit of 40 km/h would be presented as "40 km".
In W12-2, W12-2P, W21-5b, and other signs the metric unit meter should be abbreviated as "m", not "M".
The proposed metric night speed limit sign (R2-3) should appear more consistent with the daytime and truck speed limit signs (R2-1 and R2-2). My recommendations:
The use of a red circle has traditionally meant a regulatory prohibition, with or without a slash. This use is consistent with application as a maximum limit, but not in the case of a minimum speed limit.
Some may suggest the use of a green ring around the speed limit. While the MUTCD has used this for other symbolic "permissive" applications, it would be inconsistent with signage practices in countries that use the metric system, and potentially confusing to road users who are red-green color-blind.
Instead, I would recommend adopting standard European signage conventions, placing the minimum speed limit in white text in a solid blue circle.
W3-5 and W3-5a are unnecessarily "busy" signs. Surely road users could easily comprehend a sign similar to W3-1a, with the graphic of a stop sign replaced with the numeric speed in miles per hour or the numeric speed specified in a red circle with "km".
The guidance in 2C.51 should be made more explicit; I would recommend that the minimum distance should be 20 seconds' travel time at the posted speed limit prior to the speed zone.
However, I do applaud FHWA for recognizing that these signs are non-regulatory.
The guidance for "Urban Diamond Interchanges" applies to all diamond interchanges in urban areas; however, some might be confused by this usage as the Single Point Urban Interchange is sometimes referred to as an "Urban Diamond."
Lest it sound like I'm complaining, this revision also includes a number of very positive changes: