United States/Road signs/Generic shields

A print map marks U.S. Route 61 with a realistic shield but simplifies the Louisiana Highway 7 shield from to a simple .

The United States is home to hundreds of incompatible systems of numbered routes assigned by state and local authorities. Many of these systems use distinct route markers (shields) on road signs and maps specific to a particular locality. This diversity presents a challenge for any data consumer that covers the whole country or world. Traditionally, road atlases and online maps eschew the wide variety of state-specific shield designs in favor of a plain white circle for each state's primary state route network and perhaps a white rectangle for secondary state routes and county routes. These generalizations make the map more consistent, simplify the map legend, and reduce design work.

Whereas most maps are optimized for browsing at a large scale, turn-by-turn navigation software is more focused on the road ahead, making consistency across states much less important. In fact, it is more important for both the map and any guidance UI to make the same distinctions as on real-world signage. Users rarely have an opportunity to consult a legend or manual before using the software, so any discrepancy between signage and the UI could confuse the users in already stressful situations. Guidance UI typically displays much larger shields than maps, giving ample room to display more detail than a simple circle.

Counterexamples

The tables below list some representative examples of where these generalizations create problems for motorists. Together, these 15 forks or intersections are seen by an average 411,396 motorists every day (as of 2017–19), but they are only the tip of the iceberg.

Ambiguity

Here are a few representative examples of where these generalizations create ambiguity because the same number appears on two different shields at the same junction:

Location	Junction	AADT	On the ground	With generic shields
Los Angeles	State Route 57 at Interstate 210 and State Route 210 [1]	76,000		= ?
Washington, D.C.	Interstate 695 at Interstate 295 and D.C. Route 295 [2]	73,305		= ?
Rochester, New York	Interstate 490 at State Route 390 and Interstate 390 [3]	51,541		= ?
Enterprise, Nevada	Interstate 15 at Clark County Route 215 and Interstate 215 [4]	27,700		= ?
Rochester, New York	Interstate 490 at Interstate 590 and State Route 590 [5]	27,531		= ?
Cocoa Beach, Florida	Interstate 95 at State Road 528 Toll and State Road 528 [6]	16,300		= ?
Bedford, Texas	Bedford Road at State Highway 121 and State Highway 121 Toll [7]	14,439		= ?
Brainerd, Minnesota	Trunk Highway 371 at Trunk Highway 371 Business [8]	13,600		= ?
Ennis, Montana	U.S. Route 287 at Montana Highway 287 [9]	4,084		= ?
Delmont, Pennsylvania	Pennsylvania Route 66 Business at Pennsylvania Route 66 and Pennsylvania Turnpike Route 66 [10]	1,900		= ?
Tiptonville, Tennessee	State Routes 22 (primary) and 78 (primary) at State Routes 21 (primary) and 21 (secondary) [11]	332		= ?
Highspire, Pennsylvania	Interstate 283 at Pennsylvania Route 283 [12]	?		= ?

Misleading circles

Here are examples of where these generalizations can be misleading because the state uses a white circle to mark a secondary state route or county route rather than a primary state route:

Location	Junction	AADT	On the ground	With generic shields
Annandale, Virginia	State Route 236 at State Route 617 [13]	54,000		= ?
Charles Town, West Virginia	West Virginia Route 51 at County Route 13 [14]	11,573		= ?

There are also about 50 freeway junctions in Virginia and about 10 in West Virginia where a white circle can be misleading.

Misleading rectangles

Here are examples of where these generalizations can be misleading because the state uses a white rectangle to mark a primary state route rather than a secondary state route or county route:

Location	Junction	AADT	On the ground	With generic shields
Bedford, Texas	State Highway 121 at Farm to Market Road 157 [15]	20,791		= ?
DeLand, Florida	U.S. Route 17 at State Road 15A and Volusia County Road 15A [16]	18,300		15A ≠ (wrong)

There are also at least 100 freeway junctions in Texas where a white rectangle can be misleading.

See also

• United States/Road signs
• United States roads tagging/Routes
• Custom Highway Shields