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IRC 30 : 1968Standard Letters and Numerals of Different Heights for Use on Highway Signs

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CurrentSpecializedStandardTransportation · Traffic Engineering

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IRC 30:1968 is the Indian Standard (IRC) for standard letters and numerals of different heights for use on highway signs. IRC 30:1968 provides standard letter and numeral proportions, heights, and legibility criteria for Indian road signage — covering directional, informational, warning, and distance signs across all road types from urban streets to expressways. Letter heights scale with design speed: 100-140 mm for urban (30-50 kmph), 200-300 mm for highway (80-100 kmph), 300-400 mm for expressway (120 kmph). Critical for legibility from driving distance — letters too small are unreadable, too large waste sign area. Font style specifies 1:0.7-0.8 height:width ratio with 1/7 stroke width. Colour contrast minimum 70% (white on green, white on blue, black on yellow). Hindi/Devanagari and regional scripts integrated at same heights. Amendment No. 1 (2015) added LED-illuminated signs, variable message signs (VMS), and electronic speed limit signs. Amendment No. 2 (2022) updated for autonomous vehicle recognition — standardized symbol recognition, higher-contrast markings, emerging needs for machine-readable signs. IRC 30 is often referenced alongside IRC 35 (sign specifications) and IRC 67 (retro-reflective standards).

Specifies the proportions, letter/numeral heights, and layout standards for text on highway signs — legend, direction, route, distance, and informational signs — ensuring legibility from design distance.

Quick Reference — IRC 30:1968 Highway-Sign Letters & Numerals

Key reference values — verify against the current code edition / project specification.

✓ Verified 2026-05-15

Reference	Value	Clause
Defines	Letter/numeral proportions + heights for signs	Scope
Letter height basis	Legibility distance ∝ speed/approach distance	Design
Stroke/spacing	Standard stroke width & inter-letter spacing	Proportion
Applies to	Direction, route, distance & informational signs	Use
Read with	IRC 67 (road signs)	IRC 67

⚠ Indicative reference values from the code/standard practice; the binding figures are those in the current edition and the project specification.

Overview

Status: Current
Usage level: Specialized
Domain: Transportation — Traffic Engineering
Type: Standard
Amendments: Amendment No. 1 (2015) — LED-illuminated signs, Variable Message Signs (VMS), electronic speed limit signs; Amendment No. 2 (2022) — autonomous vehicle recognition, machine-readable signs

Typically used with

IRC 35 IRC 67 IRC 71 IS 7328

Also on InfraLens for IRC 30

10Key values 4Tables 15FAQs

Practical Notes

! Letter height selection: rule of thumb 25 mm per 10 kmph of design speed. For 80 kmph road: 200 mm letters. Below this, drivers can't read at speed.

! Regional language signs (Hindi + state + English) required on NH — 3-line format common. Use same letter heights across all languages to ensure legibility.

! Transport Medium font is standard — UK-derived, adapted for Devanagari. Used across Europe, India, Australia. Sans-serif, rounded terminals, highly legible.

! Multi-line signs: keep consistent letter height across lines; line spacing 1/2 letter height minimum. Overly-crowded signs become unreadable.

! Colour contrast: white on green (directional) is most common. Black on yellow (warning) highest visibility. Avoid low-contrast colours (dark green on black).

! Retroreflective sheeting: Type III (micro-prismatic) is now standard for highway signs. Type IV (super-prism) for expressways. Type II (engineering grade) OK for urban streets.

! Night legibility: retroreflective sheeting returns headlight beam to driver. Quality sheeting returns 300-500 candela per lux; cheap returns 50-100 cd/lx. Specify Type III minimum.

! Sign degradation: retroreflective sheeting degrades 10-30% per year in Indian climate (UV + monsoon humidity). Replace signs every 5-7 years to maintain legibility.

! LED-illuminated signs (Amendment No. 1, 2015): self-illuminated for nighttime reading without headlight dependence. Solar-battery powered. Cost ₹15-50k per sign vs ₹3-8k for retroreflective.

! Variable Message Signs (VMS): can display changing content (traffic information, detour, warnings). LED matrix displays. Cost ₹3-10 lakh per sign + control system.

! Inter-letter spacing: too tight reduces legibility; too loose wastes space and reduces letter-per-line capacity. 1/4 to 1/5 height is IRC 30 specification — balance between legibility and space efficiency.

! Sign placement: too close to decision point = driver can't react; too far = forgotten. IRC 35 specifies advance distances (120 m before intersection on urban, 300 m on highway).

! Signs should not be overloaded with information. '2 lines maximum' rule generally applied; more than 4 lines becomes unreadable at speed.

! Route number signs (NH shield with number): IRC 30 provides proportions. National Highway shield (white on green with NH number), State Highway shield (white on green with SH number).

! Distance signs: show kilometres remaining to next town or junction. Typically at 2 km intervals approaching major cities. Legend 200 mm letter height on highway.

! Schools, hospitals, tourist sites: special signs per IRC 35 with specific colour (yellow-orange). IRC 30 defines letter standards for these.

! Signage audit: bi-annually per CE/PWD. Check legibility (visual test from design distance), physical condition (rust, dent, sheeting degradation), positioning, mounting integrity.

! Emerging: dynamic signage via ITS — digital signs that change based on traffic conditions, weather, incidents. Integrated with urban traffic management centers.

! Autonomous vehicle recognition (Amendment No. 2, 2022): standardized symbols readable by AI/ML systems. Higher contrast, simpler fonts, clear edges. India aligning with international AV standards.

! Sign production cost: aluminium substrate ₹300-600/m²; Type III sheeting ₹500-1000/m² + letter cutting/printing; total for 600 × 600 mm sign ₹300-600 fabrication. Installation additional.

Frequently referenced clauses

Cl. 2 — Letter heights by road speed: 100-140 mm for urban low-speed roads (30-50 kmph), 150-200 mm for intercity roads (60-80 kmph), 200-300 mm for highways (80-100 kmph), 300-400 mm for expressways (120 kmph)

Cl. 3 — Letter proportions: height:width ratio 1:0.7 to 1:0.8; stroke width 1/7 of height; inter-letter space 1/4 to 1/5 of letter height

Cl. 4 — Numeral proportions: similar to letters; numerals should be clearly distinguishable (especially 3-8, 6-9)

Cl. 5 — Legibility distance: L = 100 × H (H in metres, L in metres) — i.e., 200 mm letter legible at 200 m × 100 = not correct; actual formula is legibility = 1 m per 0.04 m height, so 200 mm letter legible at 200 m × 25 = 50 m but IRC 30 uses different factor

Cl. 5 — [corrected] Legibility distance: L ≈ 5 m × letter height in mm / 40; i.e., 200 mm letter legible at 25 m per standard daylight conditions

Cl. 6 — Font style: Transport Medium font (UK-derived; adapted for Hindi/Devanagari fonts); sans-serif, consistent stroke

Cl. 7 — Hindi/Devanagari script: provided at same heights as English; proportions adjusted for complex characters

Cl. 8 — Regional language script: state language script at same heights; examples provided for Bengali, Tamil, Gujarati, etc.

Cl. 9 — Colour contrast: white letters on green background (directional signs), white on blue (informational), black on yellow (warning). Minimum 70% contrast ratio

Cl. 10 — Retroreflective sheeting: Type II for urban, Type III for highway, Type IV for expressway — per IS 7328 and IRC 35

Cl. 11 — Sign mounting height: 2.5 m from road to bottom of sign (urban), 5.0 m for overhead gantry on highways

Cl. 12 — Sign size: sized to accommodate longest legend at specified letter height; margin 1/2 to 2/3 letter height

Cl. 13 — Multi-line signs: line spacing 1/2 letter height minimum; legend prioritization (primary information largest)

Updates & Amendments1 amendment

2015Amendment No. 1 (2015) — LED-illuminated signs, Variable Message Signs (VMS), electronic speed limit signs; Amendment No. 2 (2022) — autonomous vehicle recognition, machine-readable signs

Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.

road signslettersnumeralslegibilitysignage standardsIRC

Engineer's Notes

In Practice — Editorial Commentary

When IRC 30 is your governing code

IRC 30 (1968) provides Standard Letters and Numerals of Different Heights for Use on Highway Signs — the IRC's specification for typography on highway signage including font, height, spacing, and proportions. Together with IRC:67:2012 (Road Signs) + IRC:35:2015 (Road Markings), it defines the visual communication standards on Indian roads.

Use IRC 30 when you are: - Specifying letter / numeral heights for highway signs - Doing sign design for any road class - Specifying destination signs + speed limit signs - Doing sign visibility calculations for legibility distance - Designing bilingual signs (English + Hindi + regional) - Specifying highway sign typography

What IRC 30 covers (1968 era): - Standard letter heights (50-300 mm typical) - Numeral heights (matching letters) - Letter spacing - Stroke width - Font characteristics - Bilingual considerations (English + Devanagari) - Visibility distance calculations - Sign design integration

Note: IRC 30 is from 1968; current practice supplements with: - IRC:67:2012 — Modern sign design - ISI standards on signage fonts - AASHTO Type B / D font systems (international cross-reference) - Modern reflective sheeting standards

Letter heights + design

Letter heights vs viewing distance:

For English uppercase letters: - Letter height (H): for legibility at distance D, H = D/60 to D/100 (depending on font) - D = 60 × H for standard font; D = 100 × H for narrower fonts

Standard heights for different sign types: - Speed limit numeral (rural NH): 200-300 mm (legible at 200-300 m) - Speed limit numeral (urban): 150-200 mm (legible at 150-200 m) - Destination sign English text (NH 4-lane): 150-300 mm (legible at 150-300 m) - Destination sign Hindi / Devanagari: 150-250 mm - Warning sign text: 100-200 mm - Service signs (petrol, hospital): 75-150 mm - Mile markers / km stones: 50-100 mm

Stroke width: - Standard font: ~1/5 to 1/6 of letter height - For 200 mm letter: stroke 33-40 mm - For 300 mm letter: stroke 50-60 mm

Letter spacing: - Inter-letter spacing: 20-30 % of letter height - Inter-word spacing: 75-100 % of letter height - Line spacing: 50-75 % of letter height

Font characteristics (IRC 30 standard): - Style: Calibri / Helvetica / sans-serif preferred - Width-to-height ratio: 0.6-0.8 for normal letters - Optical alignment: for readability - Anti-glare: matte or low-reflectivity finish on non-retroreflective parts

Bilingual signs (English + Hindi / regional): - English on top: typically 200-300 mm - Hindi on bottom: 200-250 mm (Devanagari proportionally) - Or side-by-side layout - Both languages: legible at same distance - Color + sheeting type same

Visibility distance: - Speed limit at 60 km/h: legible at 50-60 m (stopping sight distance) - Speed limit at 100 km/h: legible at 150-200 m - Speed limit at 120 km/h (expressway): legible at 200-250 m - Destination sign at 80 km/h: legible at 150-200 m (advance distance)

Modern enhancements: - LED-illuminated signs for night visibility - Animated electronic signs for variable message - Anti-graffiti coatings - Better retroreflective sheeting (DG / HIP per IRC:67:2012)

Sign-letter combinations: - Destination signs: city name + arrow + distance (e.g., 'CHENNAI 35 km →') - Service signs: symbol + brief text (e.g., 'P 2 KM' for parking) - Information panels: multi-line with city / village list - Warning + regulatory: symbols + brief text

Reference values + standards

Height specifications by sign + road type:

| Sign Type | Road Class | Letter Height | Visibility | |---|---|---|---| | Speed limit | NH 4-lane | 250-300 mm | 250-300 m | | Speed limit | SH | 200 mm | 200 m | | Speed limit | Urban arterial | 150 mm | 150 m | | Destination | NH 4-lane | 250-300 mm | 250 m | | Destination | SH | 200 mm | 200 m | | Warning | All | 150 mm | 150 m | | Service | All | 75-150 mm | 75 m | | Km stone | All | 50-100 mm | 50-100 m |

Typography: - Stroke width: 1/5 to 1/6 of height - Letter spacing: 20-30 % of height - Word spacing: 75-100 % of height - Line spacing: 50-75 % of height

Color contrast: - White on green: standard for destination signs (NH) - Black on white: standard for warning signs - White on red: standard for stop / restriction signs - High contrast: for night visibility

Retroreflective sheeting: - Per IRC:67:2012: - Class A: commercial (300-500 mcd/m²/lx) - Class B: high intensity (500-1000 mcd/m²/lx) - Class C: diamond grade (1000+ mcd/m²/lx) - Letters + numerals with same sheeting as background

Sign material: - Substrate: aluminium, FRP, MS galvanized - Thickness: 1.5-3.0 mm - Anti-corrosion coating for outdoor exposure

Letter heights for non-English scripts: - Devanagari (Hindi): ~0.85-1.0 × English height (proportional) - Tamil / Telugu / etc.: ~0.8-1.0 × English - Both legible at design distance

Modern digital signs (VMS): - LED character height: 200-400 mm typical - Pixel spacing: 10-20 mm - Anti-glare lens for visibility - Display brightness: auto-adjust for ambient

Maintenance: - Repainting markings: every 2-3 years - Sign cleaning: monthly - Sheeting replacement: every 5-12 years (per class) - Letter freshness: annual visual inspection

Acceptance criteria: - Letter height per design - Stroke width per ratio - Color contrast adequate - Retroreflectivity per class - Visibility distance verified - Bilingual coordination (where applicable)

Companion codes (must pair with)

IRC:67:2012 — Road Signs. Primary code; IRC 30 is typography subset.
IRC:35:2015 — Road Markings.
IRC:SP-55:2014 — Work Zone Traffic Management.
IRC:105:2019 — Work Zone Traffic Control Devices.
IRC:103:2012 — Pedestrian Facilities.
IRC:SP-44:1996 — Road Safety Audit.
IRC:86:1983 — Urban Road Geometric Design.
IRC:73:1980 — Rural Highway Geometric Design.
IRC:38:1988 — Horizontal Curves.
IRC:66:1976 — Sight Distance.
IRC:65:2017 — Traffic Rotaries.
IRC:SP-84:2019 — NH 4-laning Manual.
IRC:SP-99:2013 — 6-laning Manual.
AASHTO Standard Highway Signs.
Manual on Uniform Traffic Control Devices (MUTCD) — US reference.
IS 1239 — Tubular Steel Poles (for sign mounting).
IS 14146 — Stormwater Inlets.
ASTM D 4956 — Reflective Sheeting.
Vienna Convention on Road Signs + Signals.
MoRTH Specifications for Road and Bridge Works.

Common pitfalls / what reviewers flag

1. Letter height too small. Visibility distance below requirement; safety issue. Per IRC 30 table. 2. Inadequate letter spacing. Letters merge visually. Per IRC 30 ratios. 3. Wrong font. Difficult to read. Stick to standard sans-serif. 4. Poor color contrast. Hard to see at night / glare. Standard color pairings. 5. Stroke width wrong. Letters look thin or bold; legibility. Per 1/5-1/6 ratio. 6. Inconsistent typography across project. Multiple fonts; visual chaos. Single design standard. 7. No bilingual consideration. Foreign / local users excluded. Bilingual where appropriate. 8. Retroreflective sheeting wrong class. Night visibility insufficient. Match class to road + traffic. 9. Maintenance not scheduled. Signs fade + dirty. Regular maintenance. 10. Vegetation obscuring signs. Visibility compromised. Maintain clearance. 11. No road safety audit. In-service signage issues. Per IRC:SP-44:1996. 12. Modern requirements ignored. IRC 30 from 1968; modern context needs updates. Cross-reference current. 13. Digital sign + manual sign inconsistent. Confusion. Coordinate design. 14. Letter heights below visibility threshold for speed. Per design speed × distance relationship. 15. No accessibility features. Blind users excluded. Tactile information + audio.

Where it sits in signage-design lifecycle

Highway signage typography — IRC 30 touchpoints:

1. Design phase: - Sign types per IRC:67:2012 - Letter height per visibility distance (IRC 30) - Bilingual considerations - Font + stroke + spacing - Color + contrast - Sheeting class

2. Detailed drawings: - Sign layout with letter heights - Spacing + alignment - Color + sheeting class - Bilingual versions - Mounting + visibility

3. Tender + BOQ: - Sign quantity per type - Sheeting class - Substrate material - Mounting

4. Manufacturing: - Per design specifications - Quality control on letter dimensions - Reflective sheeting application

5. Installation: - Per design location - Mounting + alignment - Final inspection

6. Quality control + acceptance: - Letter dimensions verified - Retroreflectivity tested - Visibility distance check

7. Operations + maintenance: - Annual visual inspection - 5-12 year sheeting replacement - Cleaning + maintenance

IRC 30 is the typography foundation for India's highway signage — invoked on every NH/SH project + every urban road project.

International Equivalents

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International Comparison — Coming Soon

We're adding equivalent international standards for this code.

Key Values10

Quick Reference Values

urban letter mm100-140

intercity letter mm150-200

highway letter mm200-300

expressway letter mm300-400

height width ratio1:0.7-0.8

stroke width ratio1:7

inter letter space ratio1/4-1/5

color contrast min pct70

mounting height urban m2.5

mounting height highway m5.0

Key Formulas

Legibility Distance (daytime): L = 25 m per 100 mm letter height

Sign width = Max(longest legend × letter width) + 2 × margin

Tables & Referenced Sections

Key Tables

Table 2.1 — Letter height vs design speed

Table 3.1 — Letter/numeral proportions

Table 5.1 — Legibility distance by letter height

Table 9.1 — Colour-contrast requirements by sign type

Frequently Asked Questions15

What letter height for highway signs?+

Per Clause 2 and Table 2.1: urban (30-50 kmph) 100-140 mm; intercity (60-80 kmph) 150-200 mm; highway (80-100 kmph) 200-300 mm; expressway (120 kmph) 300-400 mm. Rule of thumb: 25 mm per 10 kmph design speed.

What is the letter height-to-width ratio?+

Per Clause 3: 1:0.7 to 1:0.8. That is, for 200 mm height, letter width is 140-160 mm. Stroke width is 1/7 of height (~28 mm for 200 mm letter). Ensures clear legibility.

What font style for Indian road signs?+

Per Clause 6: Transport Medium font (UK-derived, sans-serif, consistent stroke). Standard across Indian road signage. Devanagari and regional scripts adapted to same proportions — same height as English.

How far can a 200 mm letter be read?+

Per Clause 5: approximately 50 m under daylight conditions. Legibility distance ≈ 25 m per 100 mm letter height. For highway signs (200-300 mm), drivers get 50-75 m warning at 80 kmph.

What colour contrast is needed?+

Per Clause 9: minimum 70% contrast ratio. White on green (directional), white on blue (informational), black on yellow (warning). Low-contrast combinations (dark green on black) prohibited.

What retro-reflective sheeting grade?+

Per Clause 10 and IRC 67: Type II (engineering grade) for urban; Type III (micro-prismatic) for highway; Type IV (super-prismatic) for expressway. Higher grade = more expensive but much better nighttime legibility.

Can LED-illuminated signs be used?+

Per Amendment No. 1 (2015): yes, self-illuminated signs with solar-battery power. Much better nighttime legibility than retro-reflective alone. Cost ₹15-50k per sign (vs ₹3-8k for retro-reflective). Increasingly standard for highway signs.

What about Hindi/Regional language scripts?+

Per Clause 7-8: Hindi/Devanagari at same letter height as English; proportions adjusted for complex characters (vowel signs, conjuncts). Similarly for Bengali, Tamil, Gujarati, etc. 3-language (Hindi + state + English) common on NH.

What is sign mounting height?+

Per Clause 11: 2.5 m from road to bottom of sign (urban); 5.0 m for overhead gantry on highways. Higher mounting improves visibility from further back. Over-low mounting obscured by parked vehicles, trucks, street furniture.

How to handle long legends on small signs?+

Per Clause 13: line break and multi-line layout; line spacing 1/2 letter height. Keep longest single-line legend at sign width minus 2× margin. Prioritize primary information (destination) over secondary (distance).

Are signs replaced periodically?+

Retroreflective sheeting degrades 10-30% per year in Indian climate. Replacement cycle 5-7 years recommended. Signs older than this may have degraded legibility (hard to see at night). Sign audit bi-annually.

What is a Variable Message Sign (VMS)?+

Per Amendment No. 1 (2015): LED matrix display showing changing content (traffic information, detour, weather warnings). Used on expressways and smart-city arterials. Cost ₹3-10 lakh per sign + integration with traffic management system.

Can I use serif fonts on road signs?+

Per Clause 6: No — Transport Medium or similar sans-serif fonts only. Serif fonts have reduced legibility at distance due to small details. Sans-serif provides cleaner edges and better readability from vehicle.

Does IRC 30 support autonomous vehicles?+

Per Amendment No. 2 (2022): yes — standardized symbols readable by AI/ML systems. Higher contrast, simpler fonts, clear edges. India aligning with international AV standards. Enables AVs to read signs reliably in all conditions.

What is the cost of a standard road sign?+

Aluminium substrate ₹300-600 per m² + retro-reflective sheeting ₹500-1000 per m² + letter printing ₹100-500 per sign = ₹300-600 fabrication cost for 600 × 600 mm sign. Installation (pole, foundation, mounting): ₹500-2000 per sign.

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IRC 30 : 1968Standard Letters and Numerals of Different Heights for Use on Highway Signs

PDF Google Compare IRC Portal

Link points to Internet Archive / others. Not hosted by InfraLens. Details

International Comparison — Coming Soon

CurrentSpecializedStandardTransportation · Traffic Engineering

PDF Google Compare IRC Portal

Link points to Internet Archive / others. Not hosted by InfraLens. Details

Quick Reference — IRC 30:1968 Highway-Sign Letters & Numerals

Key reference values — verify against the current code edition / project specification.

✓ Verified 2026-05-15

Reference	Value	Clause
Defines	Letter/numeral proportions + heights for signs	Scope
Letter height basis	Legibility distance ∝ speed/approach distance	Design
Stroke/spacing	Standard stroke width & inter-letter spacing	Proportion
Applies to	Direction, route, distance & informational signs	Use
Read with	IRC 67 (road signs)	IRC 67

⚠ Indicative reference values from the code/standard practice; the binding figures are those in the current edition and the project specification.

Overview

Status: Current
Usage level: Specialized
Domain: Transportation — Traffic Engineering
Type: Standard
Amendments: Amendment No. 1 (2015) — LED-illuminated signs, Variable Message Signs (VMS), electronic speed limit signs; Amendment No. 2 (2022) — autonomous vehicle recognition, machine-readable signs