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IRC 106 : 1990Guidelines for Capacity of Urban Roads in Plain Areas

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CurrentEssentialGuidelinesTransportation · Traffic Engineering

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IRC 106:1990 is the Indian Standard (IRC) for guidelines for capacity of urban roads in plain areas. IRC 106:1990 provides capacity analysis methodology for Indian urban roads — arterials, sub-arterials, collectors, and local streets. Capacity is the maximum sustainable flow of vehicles per unit time; Level of Service (LOS) categorizes quality of flow from LOS A (free flow, v/c < 0.30) to LOS F (breakdown, v/c > 1.00). Urban target is typically LOS C (v/c 0.60-0.75). Base capacity ideal: 1800 PCU/hr per lane of 3.5 m width; urban practical 1200-1500 PCU/hr due to adjustments for narrower lanes, lateral obstructions, bus stops, cross-traffic. PHF (Peak Hour Factor) typical 0.80-0.90 for urban India — means significant peaking requiring over-design. Intersection capacity (signalized and un-signalized) typically the limiting factor in urban arterial throughput — not mid-block capacity. Amendment No. 1 (2015) added microscopic simulation methods (VISSIM, SIMTRAFFIC) for complex urban networks. Amendment No. 2 (2022) updated PCU values reflecting changed Indian vehicle mix (more 2W and cars, fewer 3W). Urban road capacity analysis is critical for: road widening decisions, traffic signal design, intersection improvements, bus lane justification, and sustainable urban transport planning.

Specifies methodology for calculation of capacity of urban roads, arterials, and streets in plain areas — including level of service analysis, saturation flow, effective width factor, and peak hour factor for traffic design.

Quick Reference — IRC 106:1990 Urban Road Capacity Numbers

Lane capacity, PCU values, level-of-service V/C ratios for urban arterials in plain terrain.

✓ Verified 2026-04-26

Reference	Value	Clause
Capacity — single lane (one-way urban arterial)	1800 PCU/h per lane	Table 5.1
Capacity — 2-lane two-way urban (single carriageway)	1500 PCU/h (both directions)	Table 5.1
Capacity — 4-lane divided urban (per direction)	3600 PCU/h	Table 5.1
Capacity — 6-lane divided urban (per direction)	5400 PCU/h	Table 5.1
PCU — passenger car / 3-wheeler	1.0 / 0.5	Table 4.1
PCU — 2-wheeler / cycle	0.5 / 0.4	Table 4.1
PCU — bus / truck (urban)	3.0	Table 4.1
PCU — LCV	1.4-2.0 (varies by gradient)
PCU — animal-drawn cart	4.0-8.0	Table 4.1
PCU — handcart / cycle rickshaw	2.0	Table 4.1
Level of Service A (free flow) — V/C ratio	≤ 0.40
LOS B (stable flow) — V/C	0.41-0.60
LOS C — V/C	0.61-0.75
LOS D — V/C	0.76-0.90
LOS E (capacity) — V/C	0.91-1.00
LOS F (forced flow / breakdown)	> 1.00 (queue forming)	Table 4
Peak hour factor — urban	0.85-0.95
Heavy vehicle adjustment — urban arterial	f-HV applied to capacity (varies)

⚠ IRC 106:1990 PCU values are widely used but newer studies (CRRI) often refine for specific cities. Verify with project-specific traffic surveys.

Overview

Status: Current
Usage level: Essential
Domain: Transportation — Traffic Engineering
Type: Guidelines
Amendments: Amendment No. 1 (2015) — microscopic simulation methods (VISSIM, SIMTRAFFIC); Amendment No. 2 (2022) — updated PCU for changed vehicle mix (more 2W/cars)

Typically used with

IRC 64 IRC 9 IRC 93 IRC SP 79

Also on InfraLens for IRC 106

10Key values 5Tables 15FAQs

Practical Notes

! LOS C (v/c 0.60-0.75) is typical urban design target. Design for LOS D in peaks; LOS E+ is congested and problematic. Major Indian cities often operate at LOS E-F during peaks.

! Mid-block capacity rarely limits urban arterials — signalized intersections are the bottleneck. Focus on intersection capacity for meaningful urban analysis.

! Peak Hour Factor (PHF) 0.80-0.90 means peak 15 minutes has 1.1-1.25× average hour volume. Design for peak, not average.

! Base capacity 1800 PCU/hr per lane is IDEAL. Urban practical: 1200-1500 PCU/hr after all adjustments. Indian conditions: lower due to heterogeneous traffic (mix of 2W, 3W, cars, trucks, buses).

! Lane width 3.5 m is standard. Narrower (3.0 m) causes 3-6% capacity reduction. Wider (4.0 m) marginal gain. Very narrow (2.75 m) typical on older roads — major capacity loss.

! Heterogeneous traffic: Indian roads have 2W (0.5 PCU), 3W (0.75 PCU), cars (1.0), buses (2.5), trucks (3.0), MAVs (4.5) all mixed. Total PCU count differs from vehicle count.

! 2W effect on capacity: high 2W proportion reduces effective capacity because 2Ws occupy less space but disturb lane discipline. Aggregate PCU analysis captures this.

! Intersection capacity: limited by green time × saturation flow. Signalized intersection typical 1800 vph per approach; un-signalized 300-900 vph.

! Signal coordination: 10-20% capacity gain on arterial via progressive green timing. Cost ₹5-15 lakh per corridor for coordination system.

! Bus bays: dedicated lane for bus stopping. Prevents bus-induced capacity loss (20-30% per stop). Cost ₹50 lakh-2 crore per bus bay.

! Cycle / pedestrian obstruction: 10-30% capacity reduction. Segregated cycle tracks (per IRC 11) mitigate this.

! Parking on urban roads: 20-40% lane capacity reduction if vehicles park on edge. Designated parking off-road preferred; parking prohibited on arterials.

! Vehicle lane discipline: Indian drivers often straddle lanes, overtake from wrong side. Reduces effective capacity below theoretical. Enforcement improves compliance.

! Micro-simulation (VISSIM, SIMTRAFFIC): models individual vehicle behavior for complex interactions. Identifies bottlenecks precisely. Cost ₹2-20 lakh per model.

! Adaptive signals (SCATS, SCOOT): real-time optimization based on traffic flow. 10-30% capacity gain over fixed timing. Investment ₹5-15 lakh per intersection.

! Urban capacity enhancement strategies: signal coordination + bus bays + signal timing + adaptive signals + micro-simulation-based design. Cumulative 30-60% capacity gain.

! Road widening as capacity solution: linear gain with lane addition but high cost and land requirement. Typically not preferred over other interventions in dense urban areas.

! Dedicated bus lanes: controversial due to perceived capacity loss but actually increases corridor capacity (buses carry more passengers per lane than cars). Delhi BRT and Mumbai BRTS examples.

! Weather impact on urban capacity: monsoon reduces capacity 20-30% due to wet pavement, reduced visibility, flooding. Design assumptions often ignore this.

! For Smart Cities Mission: real-time capacity management via ITS (adaptive signals, VMS, CCTV) gives 15-30% effective capacity gain. Much cheaper than road widening.

Frequently referenced clauses

Cl. 2 — Road classifications: Urban Arterial (50-60 kmph design, continuous flow), Sub-arterial (40-50 kmph, inter-arterial), Collector (30-40 kmph, connects local to arterial), Local Street (20-30 kmph, residential access)

Cl. 3 — Level of Service (LOS): A (free flow, v/c < 0.30), B (0.30-0.60), C (0.60-0.75, urban target), D (0.75-0.90), E (0.90-1.00, capacity), F (> 1.0, breakdown)

Cl. 4 — Base capacity (ideal conditions): 1800 PCU/hr per lane of 3.5 m width with minimum cross-traffic; 2400 PCU/hr for 2-lane one-direction; 1200-1500 for urban conditions

Cl. 5 — Adjustment factors: (a) lane width < 3.5 m — 3% reduction per 100 mm narrower; (b) lateral clearance < 1.5 m — 5% reduction per 500 mm; (c) cycle/pedestrian obstruction — 10-30% reduction

Cl. 6 — Saturation flow: ideal 1800 PCU/hr of effective green time per lane. Urban: 1400-1600 PCU/hr. Reduced by heavy vehicles (1.5× cars), grade (2% per 1% grade), and parking friction

Cl. 7 — Peak Hour Factor (PHF): ratio of hourly volume to 4 × peak 15-min volume. Urban Indian typical 0.80-0.90. Lower PHF = more peaked flow = needs over-design

Cl. 8 — Heavy vehicle PCU: 2W = 0.5, 3W = 0.75, Car = 1.0, Bus = 2.5, Truck = 3.0, MAV = 4.5 (per IRC 64). Updates for Indian vehicle mix

Cl. 9 — Intersection capacity: reduced significantly at signalized intersections. Typical urban arterial capacity limited by intersection capacity, not mid-block

Cl. 10 — Signalized intersection: Webster's formula (see IRC 93) for cycle optimization; green time allocation proportional to approach saturation flow

Cl. 11 — Un-signalized intersection: gap-acceptance theory; critical gap 6-8 seconds for side-street vehicle; capacity 300-900 vph per approach

Cl. 12 — Bus stops: absorption of 1 bus/hour reduces adjacent lane capacity by 20-30%; bus bay dedicated lanes preferred for high-volume routes

Cl. 13 — Service levels: LOS C (v/c 0.60-0.75) typical design target for urban arterials; LOS D (0.75-0.90) acceptable for peak; LOS E+ problematic

Cl. 14 — Capacity improvement: signal coordination (10-20% gain), bus bays (15-25%), lane marking (5-10%), road widening (linear with lane addition)

Cl. 15 — Modern methods: microscopic simulation (VISSIM, SIMTRAFFIC) for complex intersections; adaptive signals for real-time capacity

Updates & Amendments1 amendment

2015Amendment No. 1 (2015) — microscopic simulation methods (VISSIM, SIMTRAFFIC); Amendment No. 2 (2022) — updated PCU for changed vehicle mix (more 2W/cars)

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

capacityurban roadslevel of servicesaturation flowPHFIRC

Engineer's Notes

In Practice — Editorial Commentary

When IRC 106 is your governing code

IRC 106 provides Guidelines for Capacity of Urban Roads in Plain Areas — the IRC's standard for traffic-capacity analysis on urban arterials, sub-arterials, collectors and intersections in cities in plain (non-hilly) terrain. It is the urban-context companion to IRC SP 64:2017 (rural roads) and a critical document for urban transport planners, city DPR teams, smart-city projects, and intersection-improvement studies.

Use IRC 106 when you are: - Analysing capacity of an existing urban arterial for upgrade planning - Designing new urban roads (ring road, bypass, expressway entering city) - Studying intersection capacity (signal vs rotary vs grade-separation) - Doing traffic impact assessment (TIA) for large developments (mall, IT park, residential complex) - Evaluating smart-city street redesign for capacity vs accessibility trade-off - Comparing BRT vs general-traffic lane allocation - Doing DPR traffic chapter for urban projects - Justifying flyover / underpass at congested intersection

What IRC 106 covers: - Vehicle classification + PCU factors (urban-specific) - Capacity at different urban cross-sections (2-lane to 8-lane) - Capacity at intersections (signalised, rotary, priority) - Effect of pedestrian, parking, side-friction, signal frequency on capacity - Level of Service (LOS) classification for urban roads - Practical design service flows - Effect of bus stops, bus bays, BRT corridors - Mode-share considerations + cycle / pedestrian / bus allowances

IRC 106 is 1990 vintage — many of its specific numbers are conservative for modern Indian urban traffic. Practitioners typically supplement with: - IRC:86:1983 — geometric design of urban roads - Modern HCM-based urban capacity analysis - City-specific traffic studies - AASHTO + TRB Highway Capacity Manual For major projects, dynamic micro-simulation (PTV Vissim, SIDRA, Synchro) is now standard, with IRC 106 as the regulatory baseline.

Urban capacity context + the friction factor

Urban capacity is fundamentally different from rural capacity in three ways:

1. Frequent intersections — every 100-500 m on urban arterials; capacity is dominated by intersection delay, not free-flow speed.

2. Mixed road use — pedestrians, cycles, autos, buses, vending, parking, deliveries all share the kerb. Each subtracts from vehicle capacity.

3. Demand peaks — morning + evening peak hours intense; off-peak much lighter; capacity design must handle peak comfortably or build congestion management.

PCU factors for urban roads (IRC 106 — slightly different from rural):

| Vehicle Class | Urban PCU | |---|---| | Car / LMV / Jeep | 1.0 | | Bus | 2.2-3.0 (depending on stop-frequency) | | Truck (2-axle) | 2.5-3.0 | | 3-axle / MAV | 3.5-4.5 | | Motorised 2-wheeler | 0.5 | | Bicycle (manual) | 0.5 | | Cycle rickshaw | 1.5-2.0 | | Auto-rickshaw | 1.0 (operates close to car speed in urban) | | Hand-cart / animal cart | 4.0 |

Note: motorised 2W treated as 0.5 PCU in IRC 106 — this is reasonable for older traffic mix; modern Indian cities have 30-50 %+ 2W proportion, and observed effective PCU may be 0.3-0.4. Use site-specific calibration where 2W proportion is high.

Capacity reduction from urban friction: - Side-friction (parking, vendors, pedestrians, autos): reduces capacity by 20-50 % - Bus stop frequency: reduces capacity by 5-15 % - Intersection density: every signal at 200-300 m spacing limits effective capacity to 600-1,200 PCU/lane/hour - Driveway / minor street access: each access reduces capacity by 5-10 %

Practical service flow rate (PCU/hour) for urban arterial (mid-block, not at intersection): - LOS A: 600 PCU/lane/hr - LOS B: 900 PCU/lane/hr - LOS C: 1,200 PCU/lane/hr (design target) - LOS D: 1,400 PCU/lane/hr - LOS E (capacity): 1,500-1,600 PCU/lane/hr - LOS F: > 1,600 (over-capacity, congestion)

At signalised intersections, the limiting factor is the green time + saturation flow: - Saturation flow rate (mid-lane): 1,800-2,000 PCU/green hour - Effective lane capacity = green-ratio × saturation flow - Typical signal intersection capacity: 600-900 PCU/lane/hour

Reference values + design applications

Cross-section recommendations from IRC 106 + IRC:86 (typical):

| Road Class | Typical Cross-Section | Capacity (PCU/hour, peak) | |---|---|---| | Local street | 7-10 m wide (2-lane undivided) | 500-1,000 | | Collector | 10-14 m + footpath (2-lane divided) | 1,000-2,000 | | Sub-arterial | 16-22 m + footpath (4-lane divided) | 2,000-4,000 | | Arterial | 22-30 m + footpath (4-6 lane divided) | 4,000-6,000 | | Major arterial / expressway | 30-40 m (6-8 lane) | 6,000-10,000 |

Intersection capacity: - Priority (uncontrolled / yield): 200-500 PCU/hour through (main road); 100-300 PCU/hour minor road - Rotary (per IRC:65:2017): 1,000-5,000 PCU/hour total all approaches - Signalised: 600-900 PCU/lane/hr per phase; multi-lane multi-phase 2,000-5,000 PCU/hour - Grade-separator (flyover / underpass): unconstrained at ramp; junction capacity at base 1,000-3,000 PCU/hour

Bus capacity: - Standard 12-m city bus: 50-70 seated + standing passengers (= ~100-120 effective) - BRT-grade bus: 100-200 passengers - Bus stop spacing: 300-500 m on arterial, 200-400 m on collector - Bus stop in pull-out bay: 25-45 sec dwell per stop - Bus stop on carriageway: 30-60 sec dwell + capacity loss to following traffic

Pedestrian capacity (urban roads): - Mid-block crossing capacity: limited by signal cycle - Foot-overbridge or subway: > 5,000 pedestrians/hour - At-grade crossing: 500-1,500 pedestrians/hour per crossing point - Pedestrian sidewalk: 1,200-1,600 pedestrians/hour per metre width

Parking on-street: - Reduces effective lane width by 1-2 m - 1 lane of parking on each side of 4-lane arterial = 30-40 % capacity reduction - Parallel parking less impact than perpendicular - Designed pull-out bays minimise capacity impact

LOS service-flow for design: - Design year service flow target: LOS C in peak hour for arterials (some agencies relax to LOS D for cost reasons; not recommended for major arterials) - Off-peak service flow: typically LOS A-B (much lower demand)

Design AADT: - Peak hour percentage of daily volume: 8-15 % (lower than rural; spread out) - Annual growth rate: 3-8 % typical (lower than rural in dense cities; higher in expanding cities)

Smart-city + complete-street allocations: - Even though IRC 106 was written for vehicle capacity, modern complete-street designs allocate ROW: - Cars: 35-50 % - Public transport: 20-30 % - Cycles + pedestrians: 20-30 % - Green / landscape / utilities: 5-15 % - Vehicle capacity reduced in these designs but other-mode efficiency increased

Companion codes (must pair with)

IRC:86:1983 — Geometric Design Standards for Urban Roads in Plain Areas. Companion + cross-section.
IRC SP 64:2017 — Rural Road Capacity. Sister code for non-urban contexts.
IRC:65:2017 — Traffic Rotaries. Rotary capacity at urban junctions.
IRC:35:2015 — Road Markings. Lane discipline + capacity.
IRC:67:2012 — Road Signs.
IRC:103:2012 — Pedestrian Facilities. Pedestrian volume affects capacity.
IRC SP 90 — Grade Separators (flyovers). Capacity benefits of grade separation.
IRC SP 88 — Manual on Urban Drainage. Drainage doesn't directly affect capacity but is critical companion.
IRC SP 50:2013 — Urban Drainage Guidelines. (Note: similar number but unrelated.)
IRC SP 84 — NH 4-laning manual. NH passing through cities follows this + IRC 106.
IRC SP 12 — Reflectorisation of Markings.
IS 14146 — Stormwater Inlets.
TRB Highway Capacity Manual (HCM) — international gold standard for capacity analysis; modern projects use HCM extensively.
AASHTO Green Book — Geometric Design.
Indian Urban Transport Policy 2006 + amendments.
Smart Cities Mission urban design guidelines.
Various city Master Plan + Comprehensive Mobility Plan (CMP) documents.
ITDP (Institute for Transportation and Development Policy) BRT manuals.
Government of India MoUD Urban Transport Policy guidelines.
Direct international comparisons (e.g., London Plan, NYC Street Design Manual) — useful but adapt to Indian context.

Common pitfalls / what reviewers flag

1. PCU factors not applied to modern traffic mix. IRC 106 PCU 0.5 for 2W; observed effective is 0.3-0.4 in cities with 50 %+ 2W; over-counting 2W → undersized capacity. Use site-specific PCU calibration for high-2W cities. 2. Capacity-only design ignores access + mode share. Designer maximises vehicle throughput; reduces sidewalk / bus / cycle width; system fails for multi-modal users. Modern designs allocate ROW across modes. 3. Off-peak capacity ignored. Design for peak only; off-peak under-utilised; over-capitalised. LOS C peak + LOS A-B off-peak is reasonable balance. 4. Side friction not factored. Vendors, parked vehicles, pedestrians; capacity computed as if unrestricted; actual capacity 30 % lower. Site-specific friction observation + reduction. 5. Bus stop placement ignored. Bus stops on carriageway (not in bay); each stop = 30-60 sec capacity loss. Pull-out bays for high-frequency routes. 6. Parking allowed on arterial. On-street parking reduces capacity by 30-40 %; design AADT exceeded continuously. Designate parking bays + zones; prohibit parking on through-lanes. 7. No intersection capacity analysis. Mid-block capacity adequate; intersection capacity not analysed; intersection becomes bottleneck. Intersection-level analysis mandatory (signal warrant, rotary, grade separation). 8. TIA missing for development. Large mall / IT park added without traffic impact assessment; nearby arterial congested. TIA mandatory; mitigation measures budgeted. 9. Mode-share assumption wrong. Future mode-share assumed similar to current; metro / BRT opening changes mode-share significantly. Sensitivity analysis with multiple mode-share scenarios. 10. Pedestrian + cyclist capacity not considered. Designer focuses on vehicle capacity; pedestrian crossings + cycle lanes inadequate; safety + delay issues. Multi-modal capacity analysis. 11. Static traffic assignment. Network not modelled for dynamic flow; design for one peak scenario; performance during shoulder hours / events untested. Microsimulation for complex urban projects. 12. Cost-benefit not done. Capacity expansion proposed without comparison to demand management / mode shift / smaller upgrades. Cost-effectiveness analysis required. 13. Capacity-driven design vs accessibility / safety / equity. Modern policy emphasizes multi-modal + safe streets; pure capacity design may conflict. Balance capacity with other objectives. 14. Use of IRC 106 numbers without modern adjustment. 1990 vintage numbers conservative for some applications, optimistic for others; without modern data + sensitivity, results unreliable. Cross-check with HCM + actual site data.

Where it sits in urban-transport-planning lifecycle

Urban transport project — IRC 106 touchpoints:

1. Pre-feasibility / network planning: - City-wide travel demand estimation - Modal-share analysis - High-level corridor capacity assessment using IRC 106 - Strategic priorities (capacity vs accessibility vs safety vs equity) 2. Feasibility study: - Origin-Destination (OD) survey - Classified vehicle counts on key corridors - PCU + AADT calculation per IRC 106 - Current LOS estimation - Demand forecasting (15-20 year) - Mode-share scenarios 3. DPR + detailed traffic study: - Comprehensive traffic surveys (5-day, 24-hour with classification) - Speed-flow surveys - Side-friction + parking + pedestrian assessment - Bus + auto + intermediate public transport (IPT) inventory - Microsimulation modelling for complex corridors - Multiple design scenarios analysed 4. Geometric design: - Cross-section selection from IRC:86:1983 + capacity targets - Intersection design (signal warrant, rotary, grade separator) - Bus stop + lay-by placement - Pedestrian crossing + foot-overbridge / subway - Cycle lane / dedicated infrastructure (if specified) 5. Traffic-operations design: - Signal coordination plan - Lane discipline + marking + signage - Parking management plan - Bus priority measures (BRT, bus lanes) - One-way / two-way / restricted-direction analysis 6. TIA for major developments: - Pre-development baseline traffic - Post-development traffic with proposed land use - Mitigation measures (lane addition, signal upgrade, pedestrian facility) - Construction-phase traffic management 7. Cost-benefit + financial analysis: - User-cost reduction (travel time + vehicle operating cost) - Safety + air-quality co-benefits - Cost of intervention - Comparison with alternatives (metro, BRT, demand management) 8. Tender + BOQ: capacity-related infrastructure (signals, road widening, grade separation) quantified. 9. Construction + operations: - Phased implementation if budget-constrained - Performance monitoring: AADT + speed + LOS quarterly first year; annually thereafter - Operational adjustments (signal timing, parking enforcement) based on observed performance

IRC 106 is the regulatory foundation for urban capacity analysis in India — every state PWD, every urban planning department, every smart-city project, and every metro feeder integration uses its framework. Despite the 1990 vintage, the framework remains relevant; modern projects supplement with microsimulation + HCM + site-specific calibration.

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Key Values10

Quick Reference Values

base capacity PCU per lane hr1800

urban practical PCU per lane hr1200-1500

LOS A vc ratio< 0.30

LOS C vc ratio0.60-0.75

LOS F vc ratio> 1.00

urban PHF0.80-0.90

car PCU1.0

truck PCU3.0

bus PCU2.5

unsignalized capacity vph per approach300-900

Key Formulas

Capacity = base capacity × lane count × width adjustment × lateral clearance adjustment × friction adjustment

Volume-to-capacity ratio: v/c = volume / capacity

Peak Hour Factor: PHF = hourly volume / (4 × peak 15-min volume)

Saturation flow: s = s_0 × f_hv × f_g × f_p, where s_0 = 1800 PCU/hr, f_hv = heavy vehicle adjustment, f_g = grade adjustment, f_p = parking adjustment

Tables & Referenced Sections

Key Tables

Table 2.1 — Road classification and design parameters

Table 3.1 — Level of Service definitions

Table 4.1 — Base capacity by lane count and width

Table 5.1 — Adjustment factors

Table 8.1 — PCU values by vehicle type

Frequently Asked Questions15

What is Level of Service (LOS) on urban roads?+

Per Clause 3: categorization of flow quality. LOS A (v/c < 0.30, free flow), B (0.30-0.60), C (0.60-0.75, urban target), D (0.75-0.90, acceptable peak), E (0.90-1.00, capacity), F (> 1.0, breakdown). Most Indian metros operate at LOS E-F in peaks.

What is base capacity of urban road?+

Per Clause 4: 1800 PCU/hr per lane of 3.5 m width (ideal). Urban practical after adjustments: 1200-1500 PCU/hr. Indian heterogeneous traffic is lower due to vehicle mix.

What is Peak Hour Factor (PHF)?+

Per Clause 7: ratio of hourly volume to 4 × peak 15-minute volume. Typical urban Indian 0.80-0.90. Lower PHF = more peaked flow = peak 15 min has 1.1-1.25× average hour volume. Design for peak, not average.

What are PCU values for Indian vehicles?+

Per Clause 8 + IRC 64: 2W = 0.5, 3W = 0.75, Car = 1.0, Bus = 2.5, Truck = 3.0, MAV = 4.5. Amendment No. 2 (2022) reflects updated vehicle mix (more 2W, fewer 3W).

What is the design LOS for urban arterials?+

Per Clause 13: LOS C (v/c 0.60-0.75) typical design target. LOS D (0.75-0.90) acceptable for peaks. LOS E+ (> 0.90) congested and problematic. Design for LOS C average, accept LOS D peaks.

What limits urban arterial capacity?+

Per Clause 9: signalized intersections, not mid-block. Intersection capacity (~1800 vph per approach with good signal timing) is the bottleneck. Mid-block can handle 1400-1500 PCU/hr but signals reduce effective throughput.

How does unsignalized intersection capacity compare?+

Per Clause 11: 300-900 vph per approach depending on gap acceptance. Significantly lower than signalized (~1800 vph). Urban roads with high cross-traffic need signals; low-traffic can use roundabouts or priority rules.

How do bus stops affect capacity?+

Per Clause 12: 1 bus/hour reduces adjacent lane capacity by 20-30%. Bus bays (dedicated lanes for stopping) largely eliminate this loss. For high-volume bus corridors, bus bays essential.

Does IRC 106 cover adaptive signals?+

Per Amendment No. 1 (2015): yes — micro-simulation and adaptive signal methods. Modern practice: SCATS/SCOOT/adaptive signals provide 10-30% capacity gain over fixed timing. Smart cities increasingly deploy these.

How is road capacity calculated?+

Capacity = base capacity × lane count × width adjustment × lateral clearance adjustment × friction adjustment. Example: 2-lane arterial at 3.5 m width, 0.90 width adjustment, 0.90 friction: 1800 × 2 × 0.90 × 0.90 = 2916 PCU/hr.

How to improve urban road capacity?+

Signal coordination (10-20% gain), bus bays (15-25%), lane marking (5-10%), adaptive signals (10-30%), road widening (linear with lane addition). Cumulative 30-60% capacity gain often possible without widening.

What is saturation flow?+

Per Clause 6: 1800 PCU/hr ideal per lane of effective green time. Urban 1400-1600 PCU/hr. Reduced by heavy vehicles (each truck = 1.5× car), grades (2% per 1% grade), parking friction.

How do I calculate v/c ratio?+

v/c = volume (vph) / capacity (vph). For example: 1200 vph volume / 1600 vph capacity = 0.75, which is LOS C borderline. Use for LOS assessment.

What is the cost of urban capacity study?+

₹5-25 lakh for state arterial; ₹25 lakh-1 crore for metro city network; ₹50 lakh-5 crore for Smart Cities Mission comprehensive study. Investment critical for informed capacity decisions.

Does IRC 106 cover cycle tracks?+

Indirectly — Clause 5 adjustment for cycle obstruction (10-30% capacity reduction). Per IRC 11 + Amendment No. 1 (2022), segregated cycle tracks are preferred; mixed cycling with cars severely reduces capacity.

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IRC 106 : 1990Guidelines for Capacity of Urban Roads in Plain Areas

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Quick Reference — IRC 106:1990 Urban Road Capacity Numbers

Lane capacity, PCU values, level-of-service V/C ratios for urban arterials in plain terrain.

✓ Verified 2026-04-26

Reference	Value	Clause
Capacity — single lane (one-way urban arterial)	1800 PCU/h per lane	Table 5.1
Capacity — 2-lane two-way urban (single carriageway)	1500 PCU/h (both directions)	Table 5.1
Capacity — 4-lane divided urban (per direction)	3600 PCU/h	Table 5.1
Capacity — 6-lane divided urban (per direction)	5400 PCU/h	Table 5.1
PCU — passenger car / 3-wheeler	1.0 / 0.5	Table 4.1
PCU — 2-wheeler / cycle	0.5 / 0.4	Table 4.1
PCU — bus / truck (urban)	3.0	Table 4.1
PCU — LCV	1.4-2.0 (varies by gradient)
PCU — animal-drawn cart	4.0-8.0	Table 4.1
PCU — handcart / cycle rickshaw	2.0	Table 4.1
Level of Service A (free flow) — V/C ratio	≤ 0.40
LOS B (stable flow) — V/C	0.41-0.60
LOS C — V/C	0.61-0.75
LOS D — V/C	0.76-0.90
LOS E (capacity) — V/C	0.91-1.00
LOS F (forced flow / breakdown)	> 1.00 (queue forming)	Table 4
Peak hour factor — urban	0.85-0.95
Heavy vehicle adjustment — urban arterial	f-HV applied to capacity (varies)

⚠ IRC 106:1990 PCU values are widely used but newer studies (CRRI) often refine for specific cities. Verify with project-specific traffic surveys.

Overview

Status: Current
Usage level: Essential
Domain: Transportation — Traffic Engineering
Type: Guidelines
Amendments: Amendment No. 1 (2015) — microscopic simulation methods (VISSIM, SIMTRAFFIC); Amendment No. 2 (2022) — updated PCU for changed vehicle mix (more 2W/cars)