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Driving safety guide · Michigan City Ford · Michigan City, IN
Narrow Bridge, One Lane Bridge and Road Narrows Signs
Yellow ROAD NARROWS, NARROW BRIDGE and ONE LANE BRIDGE signs warn that the pavement, bridge, culvert or underpass ahead is narrower than usual. Here is what the federal Manual on Uniform Traffic Control Devices (MUTCD) says each one means and when it is used.
W5-1the MUTCD designation for the ROAD NARROWS sign
16 to 18 fttwo-way bridge clearance for a NARROW BRIDGE sign
Under 16 ftbridge clearance for a ONE LANE BRIDGE sign on two-way roads
Black on yellowthe standard warning sign colors, on a diamond shape
The short answer
A ROAD NARROWS sign warns that a two-lane road narrows abruptly, so oncoming vehicles cannot pass through the narrow part at the same time without slowing down. A NARROW BRIDGE sign warns of a bridge or culvert with a two-way roadway clearance of 16 to 18 feet, or narrower than the approach lanes. A ONE LANE BRIDGE sign warns of a bridge or culvert on a two-way road with a clearance of less than 16 feet, less than 18 feet where commercial vehicles make up a high proportion of the traffic, or 18 feet or less where sight distance on the approach is short.
Warning sign basics
Shape and color: except where the MUTCD designates otherwise, all warning signs shall be diamond-shaped with a black legend and border on a yellow background.
What they cover: ROAD NARROWS is about an abrupt reduction in pavement width on a two-lane road; NARROW and ONE LANE signs are tied to the roadway horizontal clearance of a bridge, culvert or underpass.
From the Manual on Uniform Traffic Control Devices (MUTCD), 11th Edition with Revision 1, Sections 2C.02 and 2C.17 to 2C.19, read November 4, 2026.
ROAD NARROWS (W5-1)
When it is used: the MUTCD says a ROAD NARROWS sign should be used in advance of a transition on two-lane roads where the pavement width is reduced abruptly to a width such that vehicles traveling in opposite directions cannot simultaneously travel through the narrow portion without reducing speed.
When it can be left off: the sign may be omitted on low-volume local streets that have speed limits of 30 mph or less.
Advisory speed: an Advisory Speed (W13-1P) plaque may be used with it to indicate the recommended speed.
From the Manual on Uniform Traffic Control Devices (MUTCD), 11th Edition with Revision 1, Section 2C.17, read November 4, 2026.
Narrow and one lane bridges
The MUTCD ties these signs to the roadway horizontal clearance of the bridge or culvert:
| Sign | When the MUTCD says it should be used |
|---|---|
| NARROW BRIDGE (W5-2) | In advance of any bridge or culvert having a two-way roadway horizontal clearance of 16 to 18 feet, or a roadway horizontal clearance less than the width of the approach travel lanes. It may also be used where the approach shoulders are narrowed or eliminated. |
| NARROW UNDERPASS (W5-2a) | Where the same conditions exist for an underpass. |
| ONE LANE BRIDGE (W5-3) | On two-way roadways in advance of any bridge or culvert with a roadway horizontal clearance of less than 16 feet; less than 18 feet when commercial vehicles make up a high proportion of the traffic; or 18 feet or less where the sight distance on the approach is less than the value in Table 2C-3 (Condition A). |
| ONE LANE UNDERPASS (W5-3a) | Where the same conditions exist for an underpass. |
From the Manual on Uniform Traffic Control Devices (MUTCD), 11th Edition with Revision 1, Sections 2C.18 and 2C.19, read November 4, 2026. The NARROW and ONE LANE signs may be omitted on low-volume rural roads where there is adequate sight distance to the bridge, culvert or underpass on both approaches.
Extra markings and plaques
Object markers and delineators: at narrow and one lane bridges, culverts and underpasses, the MUTCD says additional emphasis should be provided by object markers, delineators and/or pavement markings. At a ROAD NARROWS location, object markers and delineators may be used.
STOP or YIELD at one lane bridges: STOP (R1-1) or YIELD (R1-2) signs and related pavement markings may be used at one lane bridges and underpasses that meet the MUTCD clearance conditions. Where they are posted, follow them on your approach.
From the Manual on Uniform Traffic Control Devices (MUTCD), 11th Edition with Revision 1, Sections 2C.17 to 2C.19, read November 4, 2026.
Sign sizes
Sizes in inches from Table 2C-1 of the MUTCD:
| Sign | Single-lane conventional | Multi-lane conventional | Expressway | Freeway | Minimum |
|---|---|---|---|---|---|
| ROAD NARROWS (W5-1) | 36 x 36 | 36 x 36 | 48 x 48 | 48 x 48 | 30 x 30 |
| NARROW BRIDGE (W5-2) and NARROW UNDERPASS (W5-2a) | 36 x 36 | 36 x 36 | 48 x 48 | 48 x 48 | 30 x 30 |
| ONE LANE BRIDGE (W5-3) and ONE LANE UNDERPASS (W5-3a) | 36 x 36 | 36 x 36 | 48 x 48 | 48 x 48 | 30 x 30 |
From the Manual on Uniform Traffic Control Devices (MUTCD), 11th Edition with Revision 1, Table 2C-1, read November 4, 2026. The asterisk on these minimum sizes refers to the rule that diamond-shaped warning signs facing traffic on multi-lane conventional roads shall be at least 36 x 36 inches; Section 2C.03 applies this, with limited exceptions, where the posted speed limit is higher than 35 mph.
Keep your brakes, tires and battery ready
The Works® at Michigan City Ford includes a synthetic blend oil change, tire rotation and pressure check, brake inspection, Multi-Point Inspection, fluid top-off, battery test, and a filter, belts and hoses check.
Schedule service online and see our service specials first. Michigan City Ford is at 3930 Franklin St. in Michigan City. Get directions.
Michigan City Ford service hours
| Days | Hours |
|---|---|
| Mon-Fri | 7:30 a.m.-5:30 p.m. |
| Sat | 8 a.m.-3 p.m. |
| Sun | closed |
From Michigan City Ford's website, November 4, 2026. Holiday hours can differ.
Narrow bridge and road narrows sign FAQ
What does a ROAD NARROWS sign mean?
The ROAD NARROWS (W5-1) sign warns of a transition on a two-lane road where the pavement width is reduced abruptly, to a width at which vehicles traveling in opposite directions cannot pass through the narrow portion at the same time without reducing speed. The MUTCD says it should be used in advance of that transition, and it may be omitted on low-volume local streets with speed limits of 30 mph or less.
What does a NARROW BRIDGE sign mean?
The NARROW BRIDGE (W5-2) sign should be used in advance of any bridge or culvert with a two-way roadway horizontal clearance of 16 to 18 feet, or with a roadway horizontal clearance less than the width of the approach travel lanes. It may also be used where the approach shoulders are narrowed or eliminated.
What does a ONE LANE BRIDGE sign mean?
The MUTCD says the ONE LANE BRIDGE (W5-3) sign should be used on two-way roads in advance of a bridge or culvert with a roadway horizontal clearance of less than 16 feet; less than 18 feet when commercial vehicles make up a high proportion of traffic; or 18 feet or less where the sight distance on the approach is shorter than the MUTCD table value.
Who goes first on a one-lane bridge?
The ONE LANE BRIDGE sign is a warning sign. The MUTCD says STOP or YIELD signs and related pavement markings may be used at one-lane bridges that meet its conditions, so follow any STOP or YIELD sign on your approach.
What is a NARROW UNDERPASS or ONE LANE UNDERPASS sign?
Where the same clearance conditions exist for an underpass instead of a bridge, the MUTCD says a NARROW UNDERPASS (W5-2a) or ONE LANE UNDERPASS (W5-3a) sign should be used.
What color are these signs?
They are warning signs, so unless the MUTCD designates otherwise they are diamond-shaped with a black legend and border on a yellow background.
What does The Works at Michigan City Ford include?
The Works® at Michigan City Ford includes a synthetic blend oil change, tire rotation and pressure check, brake inspection, Multi-Point Inspection, fluid top-off, battery test, and a filter, belts and hoses check.
Book a routine checkup
Book The Works, which includes a brake inspection, tire rotation and pressure check, and battery test, at Michigan City Ford.
Sources
Sign descriptions are from the Federal Highway Administration's Manual on Uniform Traffic Control Devices, 11th Edition with Revision 1 (Revision 1 dated December 2025), read November 4, 2026. This page is a plain-language summary of national standards, not legal advice; state law sets the rules of the road where you drive. Service details, address and hours are from Michigan City Ford's own website, checked the same day. Photo is illustrative.
- Manual on Uniform Traffic Control Devices (MUTCD), 11th Edition with Revision 1 (Sections 2C.02, 2C.03 and 2C.17 to 2C.19; Table 2C-1), Federal Highway Administration, Revision 1 dated December 2025 (PDF updated February 12, 2026), read November 4, 2026
- General service: The Works, Michigan City Ford, November 4, 2026
- Address and service hours (structured data), Michigan City Ford, November 4, 2026