Determining Factors Influencing Operating Speeds on Road Tangents
Abstract
1. Introduction
2. Methodology
2.1. Research Context
2.2. Data Collection
- Dual-carriageway roads—motorways;
- Single carriageway roads:
- ⚬
- State roads,
- ⚬
- County roads.
2.2.1. Locations Selection
- Efforts were made to select locations as randomly as possible within the constraints of the road network, ensuring national representativeness and covering all major geographic regions (Central Croatia, Slavonia and Baranja, Lika, Istria, Dalmatia);
- Existing speed limit (70, 80, 90 km/h for single-carriageway roads; 100, 110, 120, 130 km/h for dual-carriageway roads). It should be noted that, in Croatia, the default speed limit outside of urban areas is 90 km/h, unless otherwise indicated by a posted speed limit sign;
- Other relevant road design, vehicle structure, road capacity, and other contributing elements;
- Speeds were measured during the week (from Monday to Friday) at off-peak hours so that the established patterns of driver behavior could be disregarded or excluded from consideration;
- To maintain data integrity and to avoid behavioral bias, all selected locations were situated away from fixed or mobile speed enforcement zones;
- Only extra-urban areas were considered to eliminate the influence of urban traffic patterns and to minimize the impact of pedestrian activity;
- Measurements were conducted exclusively on tangent segments, with a minimum tangent length of 100 m;
- Within each tangent, measurements were performed at various positions (beginning, middle, and end) to account for potential intra-segment speed variations;
- Each location also met the following geometric and environmental criteria:
- ⚬
- A straight and uniform road section, free from nearby horizontal curves that could affect vehicle speed;
- ⚬
- This study did not consider the horizontal tangents in vertical curves;
- ⚬
- A section where it is technically possible to exceed the posted speed limit;
- ⚬
- Sections exhibiting a range of longitudinal slopes (from −5.20% to +5.20% (single-carriageway roads); from −4.00% to 4.00% (dual-carriageway roads));
- ⚬
- Locations chosen across different terrain types (flat, hilly, mountainous);
- ⚬
- Locations exhibiting a variety of AADT and ASDT values.
2.2.2. Speed Measurement
- Speed Measurement—Single-carriageway Road tangents
- Speed Measurement—Dual-carriageway Road Tangents
2.2.3. Data Cleaning and Finalizing
2.2.4. Factors Identification
- Factors Identified—Single-carriageway Road Tangents
- Factors Identified—Dual-carriageway Road Tangents
2.3. Data Analysis
3. Results
3.1. Single-Carriageway Road Tangents
3.2. Dual-Carriageway Road Tangents
3.2.1. Left (Overtaking) Lane
3.2.2. Right (Driving) Lane
4. Discussion and Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
Appendix A
Road Type | Road Category | Road Name | Direction | Speed Limit [km/h] | AADT | ASDT | Total Sample Size (All Vehicle Categories) [veh] | Filtered Sample Size (Passenger Cars) [veh] | ||
---|---|---|---|---|---|---|---|---|---|---|
[veh/day] | [veh/day] | |||||||||
Single-carriageway road | State road | Dubrovnik | towards Dubrovnik | 90 | 18,292 | 25,757 | 8222 | 1024 | ||
towards Čilipi | 90 | 18,292 | 25,757 | 6802 | 1287 | |||||
Single-carriageway road | County road | Gospić | from toll | 90 | 878 | 1118 | 242 | 161 | ||
towards toll | 90 | 878 | 1118 | 176 | 119 | |||||
Single-carriageway road | County road | Knin | from Knin | 90 | 1216 | 1450 | 88 | 70 | ||
towards Knin | 90 | 1216 | 1450 | 76 | 56 | |||||
Single-carriageway road | County road | Osijek | from Osijek | 70 | 8717 | 8438 | 2433 | 933 | ||
towards Osijek | 70 | 8717 | 8438 | 3526 | 1147 | |||||
Single-carriageway road | State road | Pazin | from Pazin | 90 | 3391 | 3847 | 492 | 335 | ||
towards Pazin | 90 | 3391 | 3847 | 488 | 338 | |||||
Single-carriageway road | County road | Požega | from Požega | 90 | 1656 | 1655 | 836 | 323 | ||
towards Požega | 90 | 1656 | 1655 | 928 | 429 | |||||
Single-carriageway road | State road | Pula | from Pula | 90 | 2873 | 4375 | 1602 | 771 | ||
towards Pula | 90 | 2873 | 4375 | 1557 | 762 | |||||
Single-carriageway road | State road | Sisak | towards Sisak | 90 | 3953 | 4550 | 479 | 248 | ||
towards Stružec | 90 | 3953 | 4550 | 516 | 234 | |||||
Single-carriageway road | State road | Split | from Klis | 80 | 2404 | 3522 | 823 | 299 | ||
towards Klis | 80 | 2404 | 3522 | 1234 | 359 | |||||
Single-carriageway road | State road | Varaždin | from Varaždin | 90 | 8947 | 8773 | 1603 | 564 | ||
towards Varaždin | 90 | 8947 | 8773 | 1696 | 661 | |||||
Single-carriageway road | County road | Virovitica | from Novaki | 90 | 380 | 410 | 74 | 62 | ||
towards Novaki | 90 | 380 | 410 | 75 | 63 | |||||
Single-carriageway road | State road | Zadar | towards Zadar | 90 | 13,022 | 22,904 | 1914 | 906 | ||
towards Nin | 90 | 13,022 | 22,904 | 1211 | 502 | |||||
Total: | 37,093 | 11,653 | ||||||||
Road type | Road Category | Road name | Carriageway/Direction | Speed limit [km/h] | AADT | ASDT | Total sample size (all vehicle categories) | Filtered sample size (passenger cars) | ||
[veh/day] | [veh/day] | Left lane [veh] | Right lane [veh] | Left lane [veh] | Right lane [veh] | |||||
Dual-carriageway road | Motorway | Motorway A1 | Bisko—Blato na Cetini | 130 | 5253 | 11,059 | 391 | 739 | 86 | 113 |
Blato na Cetini—Bisko | 130 | 5253 | 11,059 | 340 | 614 | 86 | 113 | |||
Dual-carriageway road | Motorway | Motorway A1 | Bosiljevo 2—Ogulin | 100 | 10,511 | 24,747 | 414 | 600 | 94 | 106 |
Ogulin—Bosiljevo 2 | 100 | 10,511 | 24,747 | 506 | 703 | 102 | 105 | |||
Dual-carriageway road | Motorway | Motorway A1 | Donja Zdenčina—Jastrebarsko | 130 | 20,603 | 34,474 | 773 | 550 | 99 | 79 |
Jastrebarsko—Donja Zdenčina | 130 | 20,603 | 34,474 | 863 | 585 | 86 | 79 | |||
Dual-carriageway road | Motorway | Motorway A1 | Gornja Ploča—Gospić | 100 | 9255 | 22,581 | 243 | 468 | 25 | 73 |
Gospić—Gornja Ploča | 120 | 9255 | 22,581 | 443 | 688 | 82 | 114 | |||
Dual-carriageway road | Motorway | Motorway A1 | Zadar Center—Zadar East | 130 | 7857 | 19,279 | 574 | 753 | 94 | 110 |
Zadar East—Zadar Center | 130 | 7857 | 19,279 | 611 | 770 | 85 | 106 | |||
Dual-carriageway road | Motorway | Motorway A2 | Zabok—Zaprešić | 130 | 9999 | 15,473 | 137 | 355 | 29 | 86 |
Zaprešić—Zabok | 130 | 9999 | 15,473 | 232 | 502 | 43 | 108 | |||
Dual-carriageway road | Motorway | Motorway A3 | Babina Greda—Županja | 100 | 5988 | 9184 | 167 | 261 | 60 | 81 |
Županja—Babina Greda | 100 | 5988 | 9184 | 87 | 211 | 32 | 62 | |||
Dual-carriageway road | Motorway | Motorway A3 | Križ—Popovača | 130 | 13,425 | 18,067 | 242 | 443 | 52 | 72 |
Popovača—Križ | 130 | 13,425 | 18,067 | 273 | 420 | 73 | 81 | |||
Dual-carriageway road | Motorway | Motorway A3 | Lužani—Nova Gradiška | 130 | 9007 | 12,947 | 265 | 362 | 65 | 70 |
Nova Gradiška—Lužani | 130 | 9007 | 12,947 | 350 | 383 | 78 | 74 | |||
Dual-carriageway road | Motorway | Motorway A6 | Delnice—Ravna Gora | 110 | 7981 | 13,233 | 158 | 438 | 54 | 99 |
Ravna Gora—Delnice | 110 | 7981 | 13,233 | 380 | 463 | 63 | 82 | |||
Total: | 7449 | 10,308 | 1388 | 1813 | ||||||
17,757 | 3201 |
Appendix B
Operating Speed Values | Symbol | Unit of Measure | Type | Mean | StDev | Min | Max | Median |
---|---|---|---|---|---|---|---|---|
Operating speed (V85) for single-carriageway road tangents | V85 | [km/h] | Continuous | 93.18 | 14.37 | 74.00 | 128.00 | 91.50 |
Operating speed (V85) for dual-carriageway road tangents (left lane) | V85L | [km/h] | Continuous | 159.20 | 7.19 | 148.00 | 173.00 | 157.00 |
Operating speed (V85) for dual-carriageway road tangents (right lane) | V85R | [km/h] | Continuous | 142.70 | 8.22 | 131.00 | 157.00 | 141.50 |
Factors—Single-carriageway roads | Symbol | Unit of measure | Type | Mean | StDev | Min | Max | Median |
Passenger side | PS | [-] | Categorical—Multi-level; | --- | --- | --- | --- | --- |
Shoulder type | ST | [-] | Categorical—Multi-level; | --- | --- | --- | --- | --- |
Edge line quality | ELQ | [-] | Categorical—Multi-level; | --- | --- | --- | --- | --- |
Visibility | Vsb | [-] | Categorical—Multi-level; | --- | --- | --- | --- | --- |
Pavement quality | PQ | [-] | Categorical—Multi-level; | --- | --- | --- | --- | --- |
Lateral access density | LAD | [-] | Continuous | 1.63 | 1.55 | 0 | 6 | 1 |
Tangent length (up to measurement point) | TL1 | [m] | Continuous | 848.75 | 619.25 | 110.00 | 2500.00 | 715.00 |
Tangent length (from measurement point) | TL2 | [m] | Continuous | 848.75 | 619.25 | 110.00 | 2500.00 | 715.00 |
Speed limit | SL | [km/h] | Categorical—Multi-level; | 87.50 | 6.08 | 70.00 | 90.00 | 90.00 |
AADT | AADT | [veh/day] | Continuous | 5477.42 | 5488.92 | 380.00 | 18,292.00 | 3132.00 |
ASDT | ASDT | [veh/day] | Continuous | 7233.25 | 8244.36 | 410.00 | 25,757.00 | 4111.00 |
Lane width | LW | [m] | Categorical—Multi-level; | 3.02 | 0.30 | 2.50 | 3.50 | 3.00 |
Longitudinal slope | LS | [%] | Continuous | 0.00 | 3.364 | -5.20 | 5.20 | 0.00 |
Crash ratio | CR | [-] | Continuous | 0.003785 | 0.002544 | 0.002108 | 0.011545 | 0.003098 |
Design speed | Vp | [km/h] | Categorical—Multi-level; | 69.167 | 18.86 | 40.00 | 100.00 | 70.00 |
Terrain type | TT | [-] | Categorical—Multi-level; | --- | --- | --- | --- | --- |
Guardrail presence | GP | [-] | Binary | 0.17 | 0.38 | 0 | 1 | 0 |
Shoulder lane presence | ELP | [-] | Binary | 0.63 | 0.49 | 0 | 1 | 1 |
Radius of previous curve | RpC | [m] | Continuous | 418.75 | 372.51 | 25.00 | 1500.00 | 315.00 |
Radius of following curve | RfC | [m] | Continuous | 418.75 | 372.51 | 25.00 | 1500.00 | 315.00 |
Road category | RC | [-] | Binary | 0.58 | 0.50 | 0 | 1 | 1 |
Overtaking allowed | OA | [-] | Binary | 0.88 | 0.34 | 0 | 1 | 1 |
Heavy goods vehicles share | HVS | [%] | Continuous | 3.60 | 1.90 | 1.20 | 8.40 | 3.20 |
Disruptive factor presence | DFP | [-] | Binary | 0.13 | 0.34 | 0 | 1 | 0 |
Factors—Dual-carriageway roads | Symbol | Unit of measure | Type | Mean | StDev | Min | Max | Median |
Total tunnel length in last 20 km | TTL | [m] | Continuous | 274.50 | 662.05 | 0 | 2640.00 | 0 |
Speed limit | SL | [km/h] | Categorical—Multi-level; | 120.00 | 13.38 | 100.00 | 130.00 | 130.00 |
Lane width | LW | [m] | Categorical—Multi-level; | 3.70 | 0.15 | 3.25 | 3.75 | 3.75 |
Design speed | Vp | [km/h] | Categorical—Multi-level; | 116.00 | 12.31 | 80.00 | 120.00 | 120.00 |
Emergency lane presence | SLP | [-] | Binary | 0.90 | 0.31 | 0 | 1 | 1 |
Previous object distance | POD | [m] | Continuous | 4810.00 | 3066.96 | 0 | 13,400.00 | 4400.00 |
Following object distance | FOD | [m] | Continuous | 4400.00 | 3067.66 | 0 | 13,400.00 | 3650.00 |
Longitudinal slope | LS | [%] | Continuous | 0.43 | 1.81 | -4.00 | 4.00 | 0.00 |
Terrain type | TT | [-] | Categorical—Multi-level; | --- | --- | --- | --- | --- |
Heavy goods vehicles share (left lane) | HVS_LL | [%] | Continuous | 0.87 | 0.93 | 0.00 | 2.92 | 0.54 |
Heavy goods vehicles share (left lane) | HVS_RL | [%] | Continuous | 17.12 | 9.38 | 4.52 | 35.08 | 14.83 |
Heavy goods vehicles share (both lanes) | HVS_2L | [%] | Continuous | 10.53 | 5.81 | 2.56 | 22.82 | 10.09 |
AADT | AADT | [veh/day] | Continuous | 9.99 | 4.27 | 5.25 | 20.60 | 9.13 |
ASDT | ASDT | [veh/day] | Continuous | 18.10 | 7.39 | 9.18 | 34.47 | 16.77 |
Traffic flow density (left lane) | TFD_LL | [veh/km/lane] | Continuous | 2.49 | 1.42 | 0.70 | 4.80 | 2.15 |
Traffic flow density (right lane) | TFD_RL | [veh/km/lane] | Continuous | 4.33 | 1.63 | 1.80 | 7.00 | 3.80 |
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Road Name | Carriageway/Direction | Aerial Video Recording Date | Off-Peak Hour Selected for Recording |
---|---|---|---|
Motorway A1 | Bisko–Blato na Cetini | Monday, 31 July 2023 | 12:00–13:00 |
Blato na Cetini–Bisko | |||
Motorway A1 | Bosiljevo 2–Ogulin | Tuesday, 18 July 2023 | 13:00–14:00 |
Ogulin–Bosiljevo 2 | |||
Motorway A1 | Donja Zdenčina–Jastrebarsko | Tuesday, 11 July 2023 | 18:45–19:45 |
Jastrebarsko–Donja Zdenčina | |||
Motorway A1 | Gornja Ploča–Gospić | Tuesday, 18 July 2023 | 07:00–08:00 |
Gospić–Gornja Ploča | |||
Motorway A1 | Zadar Center–Zadar East | Tuesday, 8 August 2023 | 12:00–13:00 |
Zadar East–Zadar Center | |||
Motorway A2 | Zabok–Zaprešić | Tuesday, 11 July 2023 | 18:45–19:45 |
Zaprešić–Zabok | |||
Motorway A3 | Babina Greda–Županja | Monday, 24 July 2023 | 18:30–19:30 |
Županja–Babina Greda | |||
Motorway A3 | Križ–Popovača | Wednesday, 12 July 2023 | 06:00–07:00 |
Popovača–Križ | |||
Motorway A3 | Lužani–Nova Gradiška | Monday, 24 July 2023 | 13:00–14:00 |
Nova Gradiška–Lužani | |||
Motorway A6 | Delnice–Ravna Gora | Monday, 7 July 2023 | 18:30–19:30 |
Ravna Gora–Delnice |
Factors—Single-Carriageway Roads | Type | Normal Distribution | Test Used |
---|---|---|---|
Passenger side | Categorical—Multi-level | --- | ANOVA |
Shoulder type | Categorical—Multi-level | --- | ANOVA |
Edge line quality | Categorical—Multi-level | --- | ANOVA |
Visibility | Categorical—Multi-level | --- | ANOVA |
Pavement quality | Categorical—Multi-level | --- | ANOVA |
Lateral access density | Continuous | NO | Spearman |
Tangent length (up to measurement point) | Continuous | NO | Spearman |
Tangent length (from measurement point) | Continuous | NO | Spearman |
Speed limit | Categorical—Multi-level | --- | ANOVA |
AADT | Continuous | NO | Spearman |
ASDT | Continuous | NO | Spearman |
Lane width | Categorical—Multi-level | --- | ANOVA |
Longitudinal slope | Continuous | YES | Pearson |
Crash ratio | Continuous | NO | Spearman |
Design speed | Categorical—Multi-level | --- | ANOVA |
Terrain type | Categorical—Multi-level | --- | ANOVA |
Guardrail presence | Binary | --- | t-test |
Shoulder lane presence | Binary | --- | t-test |
Radius of previous curve | Continuous | NO | Spearman |
Radius of following curve | Continuous | NO | Spearman |
Road category | Binary | --- | t-test |
Overtaking allowed | Binary | --- | t-test |
Heavy goods vehicles share | Continuous | NO | Spearman |
Disruptive factor presence | Binary | --- | t-test |
Continuous Factors Single-Carriageway Roads | Test Used | Pearson Coefficient/Spearman’s ρ | Significance Level (p-Value) |
---|---|---|---|
Lateral access density | Spearman | −0.0540 | 0.8020 |
Tangent length (up to measurement point) | Spearman | 0.1076 | 0.6168 |
Tangent length (from measurement point) | Spearman | 0.1568 | 0.4643 |
AADT | Spearman | −0.3970 | 0.0547 |
ASDT | Spearman | −0.3412 | 0.1028 |
Longitudinal slope | Pearson | −0.03352 | 0.8764 |
Crash ratio | Spearman | 0.3628 | 0.0815 |
Radius of previous curve | Spearman | 0.3242 | 0.1222 |
Radius of following curve | Spearman | 0.3349 | 0.1097 |
Heavy goods vehicles share | Spearman | 0.0829 | 0.7002 |
Factors—Dual-Carriageway Roads | Type | Normal Distribution | Test Used |
---|---|---|---|
Total tunnel length in last 20 km | Continuous | NO | Spearman |
Speed limit | Categorical—Multi-level | --- | ANOVA |
Lane width | Categorical—Multi-level | --- | ANOVA |
Design speed | Categorical—Multi-level | --- | ANOVA |
Emergency lane presence | Binary | --- | t-test |
Previous object distance | Continuous | YES | Pearson |
Following object distance | Continuous | YES | Pearson |
Longitudinal slope | Continuous | YES | Pearson |
Terrain type | Categorical—Multi-level | --- | ANOVA |
Heavy goods vehicles share (left lane) | Continuous | NO | Spearman |
Heavy goods vehicles share (right lane) | Continuous | YES | Pearson |
Heavy goods vehicles share (both lanes) | Continuous | YES | Pearson |
AADT | Continuous | NO | Spearman |
ASDT | Continuous | NO | Spearman |
Traffic flow density (left lane) | Continuous | NO | Spearman |
Traffic flow density (right lane) | Continuous | YES | Pearson |
Continuous Factors Dual-Carriageway Roads—Left (Overtaking) Lane | Test Used | Pearson Coefficient/Spearman’s ρ | Significance Level (p-Value) |
---|---|---|---|
Total tunnel length in last 20 km | Spearman | −0.2194 | 0.3527 |
Previous object distance | Pearson | 0.170952 | 0.4711 |
Following object distance | Pearson | 0.188981 | 0.4249 |
Longitudinal slope | Pearson | −0.1876 | 0.4283 |
Heavy goods vehicles share (left lane) | Spearman | 0.6152 | 0.0039 * |
Heavy goods vehicles share (right lane) | Pearson | 0.115168 | 0.6287 |
Heavy goods vehicles share (both lanes) | Pearson | 0.284816 | 0.2236 |
AADT | Spearman | −0.1117 | 0.6392 |
ASDT | Spearman | −0.4649 | 0.0389 * |
Traffic flow density (left lane) | Spearman | −0.7434 | 0.0002 * |
Traffic flow density (right lane) | Pearson | −0.66612 | 0.0013 * |
Continuous Factors Dual-Carriageway Roads—Right (Driving) Lane | Test Used | Pearson Coefficient/Spearman’s ρ | Significance Level (p-Value) |
---|---|---|---|
Total tunnel length in last 20 km | Spearman | −0.2095 | 0.3754 |
Previous object distance | Pearson | 0.25115 | 0.2855 |
Following object distance | Pearson | 0.083631 | 0.7259 |
Longitudinal slope | Pearson | −0.10003 | 0.6748 |
Heavy goods vehicles share (left lane) | Spearman | 0.2591 | 0.2700 |
Heavy goods vehicles share (right lane) | Pearson | 0.25593 | 0.2761 |
Heavy goods vehicles share (both lanes) | Pearson | 0.430092 | 0.0584 |
AADT | Spearman | −0.3170 | 0.1733 |
ASDT | Spearman | −0.5525 | 0.0115 * |
Traffic flow density (left lane) | Spearman | −0.7901 | <0.0001 * |
Traffic flow density (right lane) | Pearson | −0.70432 | 0.0005 * |
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Vertlberg, J.L.; Jakovljević, M.; Abramović, B.; Ševrović, M. Determining Factors Influencing Operating Speeds on Road Tangents. Appl. Sci. 2025, 15, 7549. https://doi.org/10.3390/app15137549
Vertlberg JL, Jakovljević M, Abramović B, Ševrović M. Determining Factors Influencing Operating Speeds on Road Tangents. Applied Sciences. 2025; 15(13):7549. https://doi.org/10.3390/app15137549
Chicago/Turabian StyleVertlberg, Juraj Leonard, Marijan Jakovljević, Borna Abramović, and Marko Ševrović. 2025. "Determining Factors Influencing Operating Speeds on Road Tangents" Applied Sciences 15, no. 13: 7549. https://doi.org/10.3390/app15137549
APA StyleVertlberg, J. L., Jakovljević, M., Abramović, B., & Ševrović, M. (2025). Determining Factors Influencing Operating Speeds on Road Tangents. Applied Sciences, 15(13), 7549. https://doi.org/10.3390/app15137549