Short answer: yes, a street bench can be anchored into asphalt, but concrete is still the safer choice for a permanent outdoor bench installation. Asphalt is softer, more temperature-sensitive, and less structural than concrete. A bench anchored only into asphalt may lean, loosen, or crack the pavement over time, especially in hot weather or freeze-thaw climates. That said, if the asphalt is thick, in good condition, and the bench is not heavy or heavily used, you can anchor it successfully. The best practice on asphalt is often to use ground screws that pass through the asphalt into the compacted base below, or to cut a small section and pour a concrete pad.
Why asphalt is different from concrete: Concrete is rigid and holds mechanical anchors well. Asphalt is a flexible, bitumen-based material. In summer heat it softens; in winter it can crack. Anchors that rely on friction, like wedge anchors or sleeve anchors, do not hold as reliably in asphalt. Many anchor manufacturers do not rate their concrete anchors for asphalt. This is why a regular outdoor bench that would be fine bolted to a concrete pad may start rocking if it is bolted directly into a parking-lot or sidewalk asphalt layer.
When asphalt anchoring can work: You can get away with asphalt bench anchoring if the bench is light or medium weight, the asphalt layer is at least 3 to 4 inches thick, the area is low-vibration and low-vandalism, and the installation is temporary or semi-permanent. A wide base plate or multiple anchors will help spread the load. If you have a heavy cast-iron bench, a public street bench with constant use, or an area with extreme temperatures, plan on a concrete pad or deep ground screws.
Better methods for anchoring a street bench into asphalt: One option is a wide base plate with multiple anchors. This spreads the load across the pavement. Pre-drill holes with a masonry bit, clean out the dust, and use large washers or a base plate. Even then, check tightness regularly. Another option, and often the best one, is to use ground screws or helical anchors. These are long steel screws driven through the asphalt into the soil or gravel base below. The bench is then bolted to the screw heads, so the asphalt is not doing the real holding. The third option is to cut and pour a small concrete pad. If you want the most durable fix, cut a square out of the asphalt, dig a shallow form, pour a reinforced concrete pad a few inches thick, and anchor the bench to that with wedge anchors or cast-in-place bolts. This gives you a proper street bench concrete pad without replacing the whole area.
Step-by-step if you decide to anchor directly into asphalt: First inspect the asphalt. If it is cracked, soft, or less than 3 inches thick, do not rely on it alone. Place the bench in position and mark the holes. Drill with a hammer drill and masonry bit, and drill slightly deeper than the anchor. Clean the holes thoroughly. Install the anchors or bolts with large washers or a base plate. Tighten evenly in a star pattern. Recheck after a week or two, especially after a hot or cold spell.
Concrete pad vs asphalt at a glance: A concrete pad is very stable, has a long lifespan, and is better for public or heavy benches, but it requires more work and curing time. An asphalt anchor is faster and cheaper, and can be okay for light or temporary benches, but it needs more maintenance and has a higher risk of loosening.
Final verdict: You do not absolutely need a concrete pad for every bench. But for a street bench or any regular outdoor bench that needs to stay safe and level for years, concrete or ground screws are the professional choice. If you anchor into asphalt, treat it as a lighter-duty installation and inspect the hardware regularly.