Guidelines for Evaluating Crashworthiness of Sign Supports and Breakaway Luminaire Poles (2024)
Chapter: 8 Summary and Conclusions
CHAPTER 8
Summary and Conclusions
The objective of this project was to evaluate selected systems and propose modifications to MASH to provide additional guidelines on selecting a critical test matrix for testing families of systems. Given the time and budget constraints, the panel approved the evaluation of the two most common categories: (1) a breakaway steel luminaire pole with aluminum TB1-17 frangible transformer base, and (2) a single 2¼-in., 12-gauge PSST sign support.
8.1 Breakaway Steel Luminaire Pole with Aluminum TB1-17 Frangible Transformer Base
In Phase III, two full-scale crash tests were conducted at MwRSF.
- Tallest Pole: Case 106L: 50-ft-tall pole with dual 15-ft mast arms and weight of 1,015 lb (wall thickness of 7 gauge) to be tested under MASH Test No. 3-60 with a center impact point and a 0-degree impact angle.
- Longest Arm: Case 27: 30-ft-tall pole with single 30-ft mast arms and weight of 824 lb (wall thickness of 7 gauge) to be tested under MASH Test No. 3-60 with a center impact point and a 0-degree impact angle.
The selection of the impact point was based on the simulation results obtained during Phase II of this project. The analysis indicated that center impacts were deemed more critical than impacts at the right- or left-quarter points. Additionally, an impact angle of 0 degrees was chosen to increase the likelihood of the pole landing on the center of the roof, which has less crush stiffness. A center impact point would increase the potential for excessive roof crush compared to impact on the stiffened edges. The full-scale vehicle crash tests were evaluated according to MASH safety criteria.
In Test No. TBLP-1, the 2,413-lb 1100C small car impacted the 50-ft-tall pole with dual 15-ft-long mast arm at a speed of 19.3 mph and at an angle of 0 degrees. The TB1-17 transformer base activated in a predictable manner; however, the pole did not land on the center of the vehicle, which was the critical scenario that was anticipated. After impact, the vehicle traversed the foundation and continued forward until it stopped downstream from the system. The ORAs were within suggested limits, but the longitudinal OIV of 17.8 ft/s exceeded the MASH limit of 16 ft/s. Therefore, Test No. TBLP-1 was determined to be unacceptable according to the MASH safety performance criteria for Test No. 3-60.
In Test No. TBLP-2, the 2,426-lb 1100C small car impacted the 30-ft-tall pole with a single 30-ft-long mast arm at a speed of 19.5 mph and at an angle of 0 degrees. Upon impact, the desired breakaway activation of the TB1-17 transformer base did not occur. Instead, the vehicle rebounded after impact, a crack initiated on the left-side wall of the base and gradually extended
to the back and right-side walls of the base, and ultimately the pole fell to the right side (with respect to the impact direction) without contacting the vehicle. The ORAs were within suggested limits, but the longitudinal OIV of 31.7 ft/s exceeded the MASH limit of 16 ft/s. This behavior was primarily caused by the base not being activated during the impact event. Therefore, Test No. TBLP-2 was determined to be unacceptable according to the MASH safety performance criteria for Test No. 3-60.
Next, the LS-DYNA models were updated using the test data, material certifications, and precise transformer base measurements from the actual tests. The simulations from Phase II were validated against the results from Test Nos. TBLP-1 and TBLP-2. Subsequently, the updated models were compared with the two pendulum tests and two previously conducted full-scale crash tests at FOIL under NCHRP Project 03-119. The preliminary simulations conducted during Phase II were substantially improved and refined, particularly in predicting the OIV, a critical factor where exceedance leads to luminaire pole failures. The validated simulations showed the potential of LS-DYNA for evaluating the crashworthiness of luminaire poles in terms of OIV as one of the primary concerns associated with luminaire pole performance. Another critical aspect of breakaway poles with transformer bases is predicting base activation. In Test No. TBLP-1, the base fractured, while in Test No. TBLP-2, the base remained nonactivated. With the newly refined simulations, these two distinct behaviors were accurately predicted. This proves the model’s ability to simulate scenarios where the base remains nonactivated.
On the other hand, the inconsistent behavior of the poles after base fracture presents a challenge in predicting roof crush through simulation. Additionally, inaccuracies in the vehicle roof model introduce additional complexity to the problem. Vehicle roof models used in simulations may not always provide precise predictions of roof crush under impact conditions. As part of the continuation of the current project, these challenges will be investigated. The research team will investigate the factors contributing to the inconsistent behavior and aim to improve the accuracy of vehicle roof models used in simulations.
Note that the LS-DYNA simulations were significantly improved in predicting the impact behavior of luminaire pole devices. However, the validation process is incomplete without running the full set of tests. For instance, the simulations for luminaire poles representing MASH Test Nos. 3-61 and 3-62 impact conditions lack full-scale crash test data for validation, which makes it challenging to develop guidelines and suggest modifications to MASH for these systems.
Additionally, inconsistent behaviors were observed in the various crash tests conducted on similar pole configurations. For example, two tests were conducted at MwRSF and TTI on a 50-ft-tall pole with the TB1-17 transformer base and total weights of 1,015 lb and 730 lb, respectively. Both tests failed to meet MASH criteria, but they showed distinct behaviors. In the MwRSF test, the base fractured, causing the pole to fall on the vehicle’s roof edge, resulting in a roof crush well below the MASH limit. However, the longitudinal OIV of 17.8 ft/s exceeded the MASH limit of 16 ft/s. Conversely, in the TTI test, the pole fell on the middle of the vehicle’s roof, causing a roof crush of 6 in., which exceeded the 4-in. MASH limit. The longitudinal OIV in the TTI test measured 12.1 ft/s, which was within the MASH limit.
The second TTI test, TTI Test No. 440862-01-2, provided another instance of unexpected outcomes. This TTI test involved a system comparable to that examined in FOIL Test No. 21011. In the TTI test, a 40-ft-tall pole with 10-ft-long dual mast arms was used, while the FOIL test used a 35-ft-tall pole with longer dual mast arms extending to 20 ft. The total weights of the tested systems were 553 lb and 659 lb for TTI and FOIL, respectively. Unexpectedly, the TTI test failed to meet MASH criteria for both roof crush and OIV, while the FOIL system, with a larger weight and longer mast arms, passed all MASH criteria. These outcomes challenge the historical belief that heavier poles cause more severe damage and demonstrate that shorter or lighter poles may also lead to test failures.
The inconsistent behavior of the poles after base fracture presents challenges in predicting roof crush through simulation. Furthermore, inaccuracy in the vehicle roof model adds more complexity to the problem. Vehicle roof models used in simulations might not always provide precise predictions of roof crush when subjected to impact. These challenges will be investigated in the continuation of the current project. On a positive note, the simulations that were validated against MwRSF and FOIL tests could effectively predict the OIV as one of the two failing concerns. Given these observations, the research team would require conducting an in-depth analysis and running a comprehensive series of crash tests prior to making suggestions for reducing testing matrices for this luminaire pole family of devices. By investigating a wide range of poles and crash scenarios, the research team intends to provide more informed recommendations for luminaire poles with a TB1-17 transformer base. Thus, the concept of identifying a family and utilizing a reduced test matrix to determine crashworthiness could not be fully demonstrated.
Furthermore, with the implementation of the improved simulations, the research team conducted a rerun of simulations on revised cases to refine the recommendations made in Phase II. During Phase II, the simulations were not validated against the crash tests. However, the newly validated simulations significantly enhanced the accuracy of predictions. This approach will help identify configurations and impact conditions that are more critical. By incorporating validated simulations, the study offers more reliable insights and understanding of the crashworthiness of these devices.
Simulations on selected pole-arm configurations were conducted and are listed in Table 33. This numerical study involved the simulation of 39 steel pole configurations, covering a wide range of design parameters, including pole height (ranging from 20 ft to 50 ft) and mast arm length (ranging from 4 ft to 30 ft with both single and dual mast arms). These poles were subjected to MASH Test Numbers 3-60, 3-61, and 3-62, with varying impact points on the test vehicles, including center, left-quarter, and right-quarter points. Although the simulation results have not been fully validated against full-scale crash tests (e.g., MASH 3-61, MASH 3-62, and impacts with 25-degree impact angle and left-/right-quarter impact point), some trends have been identified in the crash performance of pole configurations under different MASH test matrices. These trends and critical impact conditions include:
- None of the simulations or full-scale crash tests exceeded MASH maximum limits for ORA values, lateral and longitudinal values, or roll and pitch values.
- Critical measures for evaluating luminaire poles include ensuring the pole base breaks away upon impact, limiting longitudinal OIV to below 16 ft/s, limiting maximum intrusion into the occupant compartment to less than 4 in., and preventing any part of the luminaire from penetrating the vehicle.
- MASH 3-60 impacts appeared to be more critical in terms of roof crush compared to MASH 3-61 and 3-62. Center impacts were found generally more critical than right- or left-quarter impacts for roof crush, primarily due to the longitudinal fall of the pole on the vehicle’s roof.
- Roof crush concerns were noted for poles weighing over 500 lb in MASH 3-60 impacts. As a result, it is recommended to conduct one full-scale crash test on any pole configuration to evaluate their performance under this critical impact condition.
- In some cases, those involving left- or right-quarter impacts at a 25-degree angle, the base did not break away, resulting in high OIV values. This behavior can be attributed to base modifications that strengthened the corners of the base. Validation through full-scale crash testing under these conditions is necessary to assess OIV criteria.
- MASH 3-61 impacts did not result in vehicle contact with the pole or intrusion of the pole into the occupant compartment.
Table 47. Draft guidelines recommended for MASH evaluation of luminaire poles with TB1-17 transformer base (not applicable before validation).
| Pole Configuration | MASH 3-60 | MASH 3-61 | MASH 3-62 |
|---|---|---|---|
| Short Poles (H ≤ 20 ft and W ≤ 450 lb) | ▶ One test needed for roof crush evaluation: 3-60-CE-0 ▶ One test needed for OIV evaluation: 3-60-RQ/LQ-25 |
No test needed | No test needed |
| Medium Poles (20 ft < H < 40 ft and W ≤ 800 lb) | ▶ One test needed for roof crush evaluation: 3-60-CE-0 ▶ One test needed for OIV evaluation: 3-60-RQ/LQ-25 |
No test needed | No test needed |
| Tall Poles (H ≥ 40 ft and W > 800 lb) | ▶ One test needed for roof crush evaluation: 3-60-CE-0 ▶ One test needed for OIV evaluation: 3-60-RQ/LQ-25 |
One test needed for OIV evaluation: 3-61-CE-0 | No test needed |
- OIV values increased as the total system weight increased in MASH 3-61 impacts, particularly for heavy poles weighing over 800 lb. Full-scale crash testing is required to determine specific critical pole characteristics.
- Center impacts at a 0-degree impact angle in MASH 3-61 appeared to be suitable for assessing OIV.
- MASH 3-62 impacts generally resulted in lower OIV values than MASH 3-61 impacts, suggesting that luminaire poles should be evaluated only under MASH 3-61 to meet OIV criteria.
- None of the MASH 3-62 impacts led to vehicle contact with the pole or intrusion into the occupant compartment. Full-scale crash tests may not be necessary for these conditions.
- Low-speed pickup truck tests were not included in the existing MASH standards. Further research is needed to assess their necessity and compare their criticality with MASH 3-60 and MASH 3-61 tests.
Based on the observations throughout full-scale crash testing and simulations, a set of recommendations for required crash tests was provided based on pole height and weight, as shown in Table 47. To validate these recommendations and to further refine the pole categories (i.e., family of devices), a series of full-scale crash tests are necessary that will also provide data for the further validation of simulations. As shown in Table 48, a minimum of seven tests are needed for validation and refinement.
Table 48. Full-scale crash tests required to validate recommendations – luminaire poles with TB1-17 transformer base.
| Pole Configuration | MASH 3-60 | MASH 3-61 | MASH 3-62 |
|---|---|---|---|
| Short Poles (H ≤ 20 ft and W ≤ 450 lb) | One test needed: 3-60-CE-0 (Roof Crush) |
No test needed | No test needed |
| Medium Poles (20 ft < H < 40 ft and W ≤ 800 lb) | Two tests needed: 3-60-CE-0 (Roof crush) 3-60-LQ/RQ-25 (OIV) |
One test needed: 3-61-CE-0 (OIV) |
No test needed |
| Tall Poles (H ≥ 40 ft and W > 800 lb) | One test needed: 3-60-LQ/RQ-25 (OIV) |
One test needed: 3-61-CE-0 (OIV) |
One test needed: 3-62-CE-0 (OIV) |
Upon validation, these recommendations may reduce the number of required tests for evaluating most luminaire poles to two or possibly one test, depending on the results of full-scale crash testing with a 25-degree impact angle. Tall and heavy poles may still require three tests but with different critical impact conditions.
Note that the current project will proceed with distinct yet aligned objectives (to NCHRP Project 17-105). The objectives of the continued research are to determine the maximum height and weight of breakaway poles and hardware that will meet MASH requirements. The research efforts will include (a) physical tests to correlate roof crush with pole and hardware height and weight and aid in determining critical pole configurations, and (b) dropping poles with associated hardware of varying heights and weights onto vehicles as a precursor to full-scale crash testing. The findings will be used to identify improvements to vehicle computer models to better simulate crash testing roof crush. Additionally, this research will investigate whether the criterion of the 4-in.-tall object on a 5-ft chord is still applicable to the current vehicle fleet. This objective should include (a) reviewing procedures used to develop the 4-in.-tall on 5-ft-chord criteria, (b) determining whether modifications or improvements to the procedure can be implemented, and (c) conducting an analysis of procedures with a current vehicle fleet. Note that the primary emphasis will be on meeting the objectives of NCHRP Project 17-105, considering how the new findings can contribute to the goals of NCHRP Project 22-43 (i.e., identifying a critical reduced matrix for MASH evaluation of luminaire poles with TB1-17 transformer base).
8.1.1 Single 2¼-in., 12-Gauge PSST Sign Support
The second type of device selected for analysis and evaluation under this project was the PSST sign support system. This system was found to be widely used across the nation, and based on the NCHRP Project 03-119 survey, it was observed to have a high rank and percentage of use by state DOTs.
The analyses began with model validations of the PSST sign support system using available full-scale crash tests. Upon completing the validations, a matrix of simulations was set up and carried out to investigate the effects of different parameters within a family of PSST sign support systems on their MASH performance. Table 49 highlights the various parameters that were investigated in the matrix of simulations. PSST systems with various panel sizes were
Table 49. PSST sign support configurations analyzed.
| Device Family | 2¼-in., 12-gauge Single PSST Sign Support | |
| Identical, Critical Structural Feature | Sign support section and size | 2¼-in., 12-gauge PSST |
| Potential Parameters That Provide Similar Safety Performance Under MASH Impact Conditions | Sign panel size (If applicable, a lower smaller advisory panel may potentially be considered.) | 1 ft × 1½ ft, 2 ft × 2 ft, 2½ ft × 2½ ft, 3 ft × 3 ft, 3 ft × 4 ft, 4 ft × 5 ft (recommended from NCHRP Project 03-119) |
| Sign panel mounting height | 7 ft (recommended from NCHRP Project 03-119) | |
| Sign panel material | Aluminum (recommended from NCHRP Project 03-119) | |
| Sign panel thickness | 0.08 in., 0.10 in., 0.12 in. | |
| Support embedment/foundation | 36 in. | |
| Presence of wind beams | With and without wind beams | |
analyzed, ranging from 1 ft × 1½ ft to 4 ft × 5 ft. Gauge thicknesses of 0.08 in., 0.1 in., and 0.12 in. were used for the sign panels, with aluminum assigned as the material for all models. The post size for this family of devices was selected to be a 2¼-in. × 2¼-in. cross-section with a gauge thickness of 12. A 7-ft mounting height to the bottom of the sign panel, the most common configuration, was used for all models. The anchor size was selected to accommodate the post sizes (2¼ in. × 2¼ in. by 12-gauge thickness), using ASTM A1011 Grade 50 steel for both the post and anchor. The anchor embedment was set at 36 in. into the ground in all models. These parameters were chosen based on what was commonly used by state DOTs determined under NCHRP Project 03-119. MASH standard soil was used for the ground surrounding the anchor. Models at three MASH impact configurations (Test Nos. 3-60, 3-61, and 3-62) were employed in the matrix of simulations. Additionally, different impact locations (center, driver-side offset, and passenger-side offset) and different impact angles (0, +25, and –25 degrees) were incorporated into the matrix of simulations.
Close to 400 simulations were performed and analyzed. A considerable amount of information was generated through the simulations. The MASH critical metrics for the PSST system were the OIV, windshield intrusion, and roof deformation. Excessive windshield penetration was by far the most common cause of failure for the PSST systems.
The results from the simulations were used to select full-scale crash tests to validate the analyses and establish guidelines for potential incorporation into MASH for testing a family of sign support devices. Five full-scale crash tests were conducted on PSST systems. All five tests used the same post: a 2¼-in., 12-gauge single PSST post, which is a criterion for belonging to the same family of devices. The five tests were diversified in terms of impact configuration (MASH Test Nos. 3-61 and 3-62), panel size (1 ft × 1.5 ft, 4 ft × 5 ft, and 3 ft × 3 ft), impact location (center and offset), and impact angle (0 and 25 degrees).
Upon analyzing the test results and comparing them with the simulation predictions, differences were observed that did not significantly affect the overall conclusions drawn from the simulation analyses. These variances were attributed to soil strength, which affected the separation timing of the post from the base sleeve. After updating the models accordingly, the simulations aligned with the test outcomes. The simulations were rerun, and the summary results were updated. Table 50 shows a summary of all cases, incorporating the results from the updated models. Based on these results, the following observations were noted:
- MASH Test No. 3-60 was the least critical of the three impacts for the family of the PSST sign support system considered. This test could be omitted or reduced to only one test with the largest sign panel.
- MASH Test No. 3-61 is the most critical of the three tests. It was noted that the size of the panel affects the MASH performance outcome. Medium-sized panels, in some cases, were more critical than smaller and larger sizes. To verify that a system with all panel sizes meets MASH, tests with the smallest and largest sign would need to be performed, and based on the outcome of these tests, an additional test may need to be performed (e.g., if the smallest panel hit the hood and the larger panel hit the roof, a test with a size in between would be needed).
- Similar effects were noted for MASH Test No. 3-62. The panel size affects the MASH performance, and the middle panel size could be more critical than the smallest and largest sizes. Testing should start with the two extreme cases (smallest and largest sizes), and based on the outcome, additional testing with in-between sizes may be needed.
- It was noted that impact locations and impact angle can have an important effect on the outcome of the test. In some cases, offset impacts and impacts at an angle were more critical than the no-offset impact. In other cases, no-offset impact was more critical. Tests with and without offset are needed.
Table 50. Summary of PSST computer simulation results.
| Impact Condition | Impact Locations and Angle | Panel Size | 1’ × 1.5’ | 2’ × 2’ | 2.5’ × 2.5’ | 3’ × 3’ | 3’ × 4’ | 4’ × 5’ | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Panel Thickness | 0.08 | 0.10 | 0.12 | 0.08 | 0.10 | 0.12 | 0.08 | 0.10 | 0.12 | 0.08 | 0.10 | 0.12 | 0.08 | 0.10 | 0.12 | 0.08 | 0.10 | 0.12 | ||
| MASH 3-60 | Center/0 Deg. | OIV (ft/s) | 5.2 | 5.6 | 5.6 | 6.6 | 7.2 | 7.2 | 7.9 | 8.2 | 8.2 | |||||||||
| Windshield Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |||||||||||
| Roof Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |||||||||||
| Driver-Side Offset/0-Deg. | OIV (ft/s) | 5.9 | 5.9 | 6.2 | 7.2 | 7.5 | 7.9 | 7.9 | 8.5 | 8.5 | 8.9 | 9.2 | 9.5 | 9.5 | 9.8 | 10.5 | 11.2 | 11.5 | 11.8 | |
| Windshield Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ||
| Roof Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ||
| Pass.-Side Offset/0 Deg. | OIV (ft/s) | 5.9 | 5.9 | 5.9 | 7.2 | 7.5 | 7.9 | 8.2 | 8.5 | 8.9 | ||||||||||
| Windshield Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |||||||||||
| Roof Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |||||||||||
| MASH 3-61 | Center/0 Deg. | OIV (ft/s) | 3.3 | 6.2 | 6.6 | 6.2 | 6.2 | 6.9 | 6.2 | 5.9 | 6.2 | 6.2 | 5.9 | 3.9 | ||||||
| Windshield Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 1.2T | 4.7T | 8.8T | 8.2T | 4.3T | 0 | ||||||||
| Roof Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2.8 | 4.3 | 4.3 | 3.9 | 5.9 | ||||||||
| Center/–25 Deg. | OIV (ft/s) | 5.9 | 5.6 | 6.2 | 6.6 | 6.2 | 6.2 | 6.2 | 3.0 | 6.6 | 6.2 | 7.2 | 4.9 | |||||||
| Windshield Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0.7T | 4.3T | 1.2T | 3.1T | 3.1T | 6.7T | 3.3T | ||||||||
| Roof Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 2.362 | 0 | 1.6 | 1.6 | 3.9 | 8.0 | ||||||||
| Center/+25 Deg. | OIV (ft/s) | 4.9 | 5.9 | 5.2 | 5.6 | 5.6 | 7.2 | 7.2 | 7.9 | 7.2 | 7.2 | 3.3 | 6.2 | |||||||
| Windshield Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0.4T | 1.6T | 2.0T | 3.1T | 1.8T | 6.3T | 7.9T | ||||||||
| Roof Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 2.4 | 0 | 0 | 0 | 3.6 | 5.1 | ||||||||
| Driver-Side Offset/0 Deg. | OIV (ft/s) | 3.3 | 3.6 | 3.3 | 2.6 | 2.6 | 2.6 | 2.6 | 2.6 | 2.6 | 2.6 | 2.6 | 1.0 | |||||||
| Windshield Int. (in.) | 1.2T | 1.6T | 4.2T | 12.4T | 6.8T | 12.5T | 13.0T | 11.8T | 4.7T | 4.7T | 4.1T | 0.1 | ||||||||
| Roof Int. (in.) | 0 | 0 | 0.2 | 3.9 | 0.2 | 4.3 | 3.9 | 3.9 | 3.5 | 3.9 | 3.3 | 2.4 | ||||||||
| Pass.-Side Offset/0 Deg. | OIV (ft/s) | |||||||||||||||||||
| Windshield Int. (in.) | ||||||||||||||||||||
| Roof Int. (in.) | ||||||||||||||||||||
| MASH 3-62 | Center/0 Deg. | OIV (ft/s) | 2.0 | 2.0 | 2.3 | 2.3 | 2.6 | 2.3 | 1.3 | 2.3 | 2.3 | 2.3 | 2.3 | 2.3 | ||||||
| Windshield Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3.9 | 5.5 | 0 | 5.5 | 3.3 | 0 | 3.6 | ||||||
| Roof Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 4.7 | 2.4 | 0 | 3.0 | 3.2 | 0 | 3.504 | ||||||
| Center/+25 Deg. | OIV (ft/s) | 1.6 | 2.0 | 2.0 | 3.0 | 3.9 | 3.0 | 1.6 | 3.0 | 1.6 | 3.3 | 3.0 | 3.0 | |||||||
| Windshield Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3.9 | 2.8 | 0 | 2.4 | 1.8 | 0 | 2.205 | ||||||
| Roof Int. (in.) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0.8 | 0 | 1.6 | 2.8 | 0 | 3.0 | ||||||
| Center/–25 Deg. | OIV (ft/s) | |||||||||||||||||||
| Windshield Int. (in.) | ||||||||||||||||||||
| Roof Int. (in.) | ||||||||||||||||||||
Notes: 
= meets MASH criteria; 
= does not meet MASH criteria; “T” after intrusion number indicates tearing is predicted; Int. = intrusion; blank cells, green or red, represent cases that were not run but their outcome was assessed based on results from the other simulations.
Table 51. Original MASH test matrix for support structures (AASHTO 2016).
| Feature | Test No. | Vehicle | Impact Speeda [mph (km/h)] |
Impact Angleb (θ deg.) | Acceptable KE Range [kip-ft (kJ)] |
Impact Point | Evaluation Criteriac |
|---|---|---|---|---|---|---|---|
| Support Structures | 3-60 | 1100C | 19 (30) | 25 | ≤34 (41) | (c) | B, D, F, H, I, N |
| 3-61 | 1100C | 62 (100) | 25 | ≥288 (390) | (c) | B, D, F, H, I, N | |
| 3-62 | 2270P | 62 (100) | 25 | ≥594 (806) | (c)t | B, D, F, H, I, N |
Notes: a See MASH Section 2.1.2 for tolerances on impact conditions; b see MASH Table 5-1; c see MASH Figure 2-5 for impact point.
Table 52. Recommended test matrix for family of PSST sign support systems.
| Feature | Test No. | Vehicle | Family System Sizea | Impact Speed [mph (km/h)]b | Impact Anglec (θ deg.) | Acceptable KE Range [kip-ft (kJ)] | Impact Pointd | Evaluation Criteriae |
|---|---|---|---|---|---|---|---|---|
| Small-Sign Support System | 3-60A | 1100C | Tallest | 19 (30) | 25 | ≤34 (41) | Offset | B, D, F, H, I, N |
| 3-61A | 1100C | Tallest | 62 (100) | 25 | ≥288 (390) | Center | B, D, F, H, I, N | |
| 3-61B | 1100C | Shortest | 62 (100) | 25 | ≥288 (390) | Offset | B, D, F, H, I, N | |
| 3-61Cf | 1100C | Midsize | 62 (100) | 25 | ≥288 (390) | Offset | B, D, F, H, I, N | |
| 3-62A | 2270P | Tallest | 62 (100) | 25 | ≥594 (806) | Center | B, D, F, H, I, N | |
| 3-62B | 2270P | Shortest | 62 (100) | 25 | ≥594 (806) | Offset | B, D, F, H, I, N | |
| 3-62Cf | 2270P | Midsize | 62 (100) | 25 | ≥594 (806) | Offset | B, D, F, H, I, N |
Notes: a See report Sections 7.2.3 and 7.2.4 for size guidance; b see MASH Section 2.1.2 for impact conditions tolerances; c see report Section 7.2.6 for impact angle; d see report Section 7.2.5 for impact location; e see MASH Table 5-1 for evaluation criteria; f may not be required (see Sections 7.2.3 and 7.2.4).
Considering all impacts, none of the configurations analyzed were found to meet the MASH criteria for all three tests (3-60, 3-61, and 3-62). This highlights the difficulty of developing a system that meets current MASH criteria.
A matrix of tests is currently defined in MASH for sign support systems (see Table 51). Running this matrix for all possible configurations of a family of PSST systems would be cost-prohibitive. Using the results from the simulations, along with the full-scale crash tests and insights gained from existing literature, the research team developed a matrix for MASH testing a family of PSST sign support systems. Instead of running the three impacts (3-60, 3-61, and 3-62) for each configuration in the family of devices, the new matrix incorporates fewer key tests on select critical configurations. The new matrix reduces the number of required tests without compromising the evaluation and safety of the different configurations within the PSST family of devices. Table 52 depicts the updated test matrix for the family of PSST systems analyzed. Only Test Level 3 is included in the table, but similar tests can be adopted for the other test levels. The same table can be adopted for other small-sign support systems after further analyses and testing.
The impact speeds, test vehicles, and evaluation criteria remained unchanged from the original MASH recommendations. The impact angles and locations were updated to reflect worst-case scenarios. According to the revised matrix, a minimum of five tests are needed for each family of devices, with the possibility of requiring two additional tests depending on the outcomes of the initial five tests.
